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Cooper pair formation in trapped atomic Fermi gases
Houbiers, M.; Stoof, H.T.C.
We apply the closed time-path formalism to evaluate the dynamics of the BCS transition to the superfluid state in trapped atomic 6-Li. We find that the Fokker-Planck equation for the propability distribution of the order parameter is, sufficiently close to the critical temperature, identical to the
Cooper-pair formation in trapped atomic Fermi gases
Houbiers, M.; Stoof, H.T.C.
We apply the Schwinger-Keldysh formalism to study the nonequilibrium dynamics of the BCS transition to the superfluid state in trapped atomic 6Li. We find that the Fokker-Planck equation for the probability distribution of the order parameter is, sufficiently close to the critical temperature,
Topological Fulde-Ferrell superfluid in spin-orbit-coupled atomic Fermi gases
Liu, Xia-Ji; Hu, Hui
We theoretically predict a topological matter—topological inhomogeneous Fulde-Ferrell superfluid—in one-dimensional atomic Fermi gases with equal Rashba and Dresselhaus spin-orbit coupling near s-wave Feshbach resonances. The realization of such a spin-orbit-coupled Fermi system has already been demonstrated recently by using a two-photon Raman process and the extra one-dimensional confinement is easy to achieve using a tight two-dimensional optical lattice. The topological Fulde-Ferrell superfluid phase is characterized by a nonzero center-of-mass momentum and a nontrivial Berry phase. By tuning the Rabi frequency and the detuning of Raman laser beams, we show that such an exotic topological phase occupies a significant part of parameter space and therefore it could be easily observed experimentally, by using, for example, momentum-resolved and spatially resolved radio-frequency spectroscopy.
I.I. Rabi in Atomic, Molecular & Optical Physics Prize Talk: Strongly Interacting Fermi Gases of Atoms and Molecules
Zwierlein, Martin
Strongly interacting fermions govern physics at all length scales, from nuclear matter to modern electronic materials and neutron stars. The interplay of the Pauli principle with strong interactions can give rise to exotic properties that we do not understand even at a qualitative level. In recent years, ultracold Fermi gases of atoms have emerged as a new type of strongly interacting fermionic matter that can be created and studied in the laboratory with exquisite control. Feshbach resonances allow for unitarity limited interactions, leading to scale invariance, universal thermodynamics and a superfluid phase transition already at 17 Trapped in optical lattices, fermionic atoms realize the Fermi-Hubbard model, believed to capture the essence of cuprate high-temperature superconductors. Here, a microscope allows for single-atom, single-site resolved detection of density and spin correlations, revealing the Pauli hole as well as anti-ferromagnetic and doublon-hole correlations. Novel states of matter are predicted for fermions interacting via long-range dipolar interactions. As an intriguing candidate we created stable fermionic molecules of NaK at ultralow temperatures featuring large dipole moments and second-long spin coherence times. In some of the above examples the experiment outperformed the most advanced computer simulations of many-fermion systems, giving hope for a new level of understanding of strongly interacting fermions.
Pseudospin pairing and transport in atomic Fermi gases and bilayer systems
Mink, M.P.
In this Thesis we consider the behavior of the drag conductivity close to exciton condensation in bilayer systems and close to the superfluid transition in cold Fermi gases. In chapter 2 we calculate the transition temperature for exciton condensation in double-layer graphene, showing that the
Strongly interacting Fermi gases
Directory of Open Access Journals (Sweden)
Bakr W.
Full Text Available Strongly interacting gases of ultracold fermions have become an amazingly rich test-bed for many-body theories of fermionic matter. Here we present our recent experiments on these systems. Firstly, we discuss high-precision measurements on the thermodynamics of a strongly interacting Fermi gas across the superfluid transition. The onset of superfluidity is directly observed in the compressibility, the chemical potential, the entropy, and the heat capacity. Our measurements provide benchmarks for current many-body theories on strongly interacting fermions. Secondly, we have studied the evolution of fermion pairing from three to two dimensions in these gases, relating to the physics of layered superconductors. In the presence of p-wave interactions, Fermi gases are predicted to display toplogical superfluidity carrying Majorana edge states. Two possible avenues in this direction are discussed, our creation and direct observation of spin-orbit coupling in Fermi gases and the creation of fermionic molecules of 23Na 40K that will feature strong dipolar interactions in their absolute ground state.
Spin-orbit coupled two-electron Fermi gases of ytterbium atoms
Song, Bo; Zhang, Shanchao; Zou, Yueyang; Haciyev, Elnur; Huang, Wei; Liu, Xiong-Jun; Jo, Gyu-Boong
We demonstrate the spin-orbit coupling (SOC) in a two-electron Fermi gas of $^{173}$Yb atoms by coupling two hyperfine ground states via the two-photon Raman transition. Due to the SU($N$) symmetry of the $^1$S$_0$ ground-state manifold which is insensitive to external magnetic field, an optical AC Stark effect is applied to split the ground spin states and separate an effective spin-1/2 subspace out from other hyperfine levels for the realization of SOC. With a momentum-dependent spin-orbit gap being suddenly opened by switching on the Raman transition, the dephasing of spin dynamics is observed, as a consequence of the momentum-dependent Rabi oscillations. Moreover, the momentum asymmetry of the spin-orbit coupled Fermi gas is also examined after projection onto the bare spin state and the corresponding momentum distribution is measured for different two-photon detuning. The realization of SOC for Yb fermions may open a new avenue to the study of novel spin-orbit physics with alkaline-earth-like atoms.
Hydrodynamics of unitary Fermi gases
Young, Ryan E.
Unitary fermi gases have been widely studied as they provide a tabletop archetype for re- search on strongly coupled many body systems and perfect fluids. Research into unitary fermi gases can provide insight into may other strongly interacting systems including high temperature superconductor, quark-gluon plasmas, and neutron stars. Within the unitary regime, the equilib- rium transport coefficients and thermodynamic properties are universal functions of density and temperature. Thus, unitary fermi gases provide a archetype to study nonperturbative many-body physics, which is of fundamental significance and crosses several fields. This thesis reports on two topics regarding unitary fermi gases. A recent string theory conjecture gives a lower bound for the dimensionless ratio of shear viscosity of entropy, η/s ≥ 4pi /kb . Unitary fermi gases are a candidate for prefect fluids, yet η/s is well above the string theory bound. Using a stochastic formulation of hydrodynamics, we calculate a lower bound for this ratio accounting for the momentum dissipation from fluctuations. This lower bound is in good agreement with both theoretical and experimental results. The second question addressed is the simulation of elliptic flow. Elliptic flow, first observed in 2002, is a characteristic of strongly coupled systems and has been studied in both quark-gluon plasmas and unitary fermi gases. As such, simulations of these systems are of interest. We test a variety of lattice Boltzmann models and compare the simulation results to the theoretical and experimental findings.
Spin-orbit coupling in ultracold Fermi gases of 173Yb atoms
Song, Bo; He, Chengdong; Hajiyev, Elnur; Ren, Zejian; Seo, Bojeong; Cai, Geyue; Amanov, Dovran; Zhang, Shanchao; Jo, Gyu-Boong
Synthetic spin-orbit coupling (SOC) in cold atoms opens an intriguing new way to probe nontrivial topological orders beyond natural conditions. Here, we report the realization of the SOC physics both in a bulk system and in an optical lattice. First, we demonstrate two hallmarks induced from SOC in a bulk system, spin dephasing in the Rabi oscillation and asymmetric atomic distribution in the momentum space respectively. Then we describe the observation of non-trivial spin textures and the determination of the topological phase transition in a spin-dependent optical lattice dressed by the periodic Raman field. Furthermore, we discuss the quench dynamics between topological and trivial states by suddenly changing the band topology. Our work paves a new way to study non-equilibrium topological states in a controlled manner. Funded by Croucher Foundation and Research Grants Council (RGC) of Hong Kong (Project ECS26300014, GRF16300215, GRF16311516, and Croucher Innovation Grants).
DEFF Research Database (Denmark)
Bruun, Georg
We examine spin diffusion in a two-component homogeneous Fermi gas in the normal phase. Using a variational approach, analytical results are presented for the spin diffusion coefficient and the related spin relaxation time as a function of temperature and interaction strength. For low temperatures...
Itinerant Ferromagnetism in Ultracold Fermi Gases
DEFF Research Database (Denmark)
Heiselberg, Henning
Itinerant ferromagnetism in cold Fermi gases with repulsive interactions is studied applying the Jastrow-Slater approximation generalized to finite polarization and temperature. For two components at zero temperature a second order transition is found at akF ≃ 0.90 compatible with QMC. Thermodyna......Itinerant ferromagnetism in cold Fermi gases with repulsive interactions is studied applying the Jastrow-Slater approximation generalized to finite polarization and temperature. For two components at zero temperature a second order transition is found at akF ≃ 0.90 compatible with QMC...... for effective separation of large ferromagnetic domains. Collective modes are predicted and tri-critical points are calculated for multi-component systems....
Current reversals in rapidly rotating ultracold Fermi gases
Bencheikh, K.; Medjedel, S.; Vignale, G.
We study the equilibrium current density profiles of harmonically trapped ultracold Fermi gases in quantum Hall-like states that appear when the quasi-two-dimensional trap is set in fast rotation. The density profile of the gas (in the rotating reference frame) consists of incompressible strips of constant quantized density separated by compressible regions in which the density varies. Remarkably, we find that the atomic currents flow in opposite directions in the compressible and incompressible regions—a prediction that should be amenable to experimental verification.
Quantum information entropies of ultracold atomic gases in a ...
Indian Academy of Sciences (India)
The position and momentum space information entropies of weakly interacting trapped atomic Bose–Einstein condensates and spin-polarized trapped atomic Fermi gases at absolute zero temperature are evaluated. We find that sum of the position and momentum space information entropies of these quantum systems ...
Metastability in spin polarised Fermi gases and quasiparticle decays
DEFF Research Database (Denmark)
Sadeghzadeh, Kayvan; Bruun, Georg; Lobo, Carlos
We investigate the metastability associated with the first order transition from normal to superfluid phases in the phase diagram of two-component polarised Fermi gases.We begin by detailing the dominant decay processes of single quasiparticles.Having determined the momentum thresholds of each pr...
Cooling Atomic Gases With Disorder
Paiva, Thereza; Khatami, Ehsan; Yang, Shuxiang; Rousseau, Valéry; Jarrell, Mark; Moreno, Juana; Hulet, Randall G.; Scalettar, Richard T.
Cold atomic gases have proven capable of emulating a number of fundamental condensed matter phenomena including Bose-Einstein condensation, the Mott transition, Fulde-Ferrell-Larkin-Ovchinnikov pairing, and the quantum Hall effect. Cooling to a low enough temperature to explore magnetism and exotic superconductivity in lattices of fermionic atoms remains a challenge. We propose a method to produce a low temperature gas by preparing it in a disordered potential and following a constant entropy trajectory to deliver the gas into a nondisordered state which exhibits these incompletely understood phases. We show, using quantum Monte Carlo simulations, that we can approach the Néel temperature of the three-dimensional Hubbard model for experimentally achievable parameters. Recent experimental estimates suggest the randomness required lies in a regime where atom transport and equilibration are still robust.
Microscopy of 2D Fermi gases. Exploring excitations and thermodynamics
Energy Technology Data Exchange (ETDEWEB)
Morgener, Kai Henning
This thesis presents experiments on three-dimensional (3D) and two-dimensional (2D) ultracold fermionic {sup 6}Li gases providing local access to microscopic quantum many-body physics. A broad magnetic Feshbach resonance is used to tune the interparticle interaction strength freely to address the entire crossover between the Bose-Einstein-Condensate (BEC) and Bardeen-Cooper-Schrieffer (BCS) regime. We map out the critical velocity in the crossover from BEC to BCS superfluidity by moving a small attractive potential through the 3D cloud. We compare the results with theoretical predictions and achieve quantitative understanding in the BEC regime by performing numerical simulations. Of particular interest is the regime of strong correlations, where no theoretical predictions exist. In the BEC regime, the critical velocity should be closely related to the speed of sound, according to the Landau criterion and Bogolyubov theory. We measure the sound velocity by exciting a density wave and tracking its propagation. The focus of this thesis is on our first experiments on general properties of quasi-2D Fermi gases. We realize strong vertical confinement by generating a 1D optical lattice by intersecting two blue-detuned laser beams under a steep angle. The large resulting lattice spacing enables us to prepare a single planar quantum gas deeply in the 2D regime. The first measurements of the speed of sound in quasi-2D gases in the BEC-BCS crossover are presented. In addition, we present preliminary results on the pressure equation of state, which is extracted from in-situ density profiles. Since the sound velocity is directly connected to the equation of state, the results provide a crosscheck of the speed of sound. Moreover, we benchmark the derived sound from available equation of state predictions, find very good agreement with recent numerical calculations, and disprove a sophisticated mean field approach. These studies are carried out with a novel apparatus which has
Comparing and contrasting nuclei and cold atomic gases
DEFF Research Database (Denmark)
Zinner, Nikolaj Thomas; Jensen, Aksel Stenholm
The experimental revolution in ultracold atomic gas physics over the past decades has brought tremendous amounts of new insight to the world of degenerate quantum systems. Here we compare and contrast the developments of cold atomic gases with the physics of nuclei since many concepts, techniques...... (BEC) and Bardeen–Cooper–Schrieffer (BCS) theory, as well as the BCS–BEC crossover and the Fermi gas in the unitarity limit, all within the context of ultracold atoms. Subsequently, we consider the specific example of an atomic Fermi gas from a nuclear physics perspective, comparing degrees of freedom......, with advances in the trapping of few-body atomic systems we expect a more direct exchange of ideas and results....
Universal properties of Fermi gases in arbitrary dimensions
DEFF Research Database (Denmark)
Valiente, Manuel; T. Zinner, Nikolaj; Molmer, Klaus
We consider spin-1/2 Fermi gases in arbitrary, integer or non-integer spatial dimensions, interacting via a Dirac delta potential. We first generalize the method of Tan's distributions and implement short-range boundary conditions to arbitrary dimension and we obtain a set of universal relations...... for the Fermi gas. Three-dimensional scattering under very general conditions of transversal confinement is described by an effectively reduced-dimensional scattering length, which we show depends on the three-dimensional scattering length in a universal way. Our formula for non-integer dimensions interpolates...
Quantum Degenerate Gases of Atomic Strontium
Killian, T. C.
This talk will describe the production and properties of a Bose-Einstein condensate of ^84Sr and a quantum degenerate mixture of ^87Sr (fermion) and ^88Sr (boson). ^88Sr has a small negative scattering length leading to a maximum condensate size for our trapping conditions of about 10^4 atoms. ^87Sr is used to sympathetically cool ^88Sr, but it is also of interest for study of quantum degenerate Fermi gases because it has a large nuclear spin (I=9/2). Alkaline-earth metal atoms and atoms with similar electronic structure are of interest for quantum computing proposals, cold collision studies, and investigation of quantum fluids. There are a wealth of isotopes that allow mass-tuning of interactions and creation of various quantum mixtures. The two-valence electrons lead to a singlet ground state and narrow intercombination transitions to metastable triplet states, offering the promise of low-loss optical Feshbach resonances for manipulating scattering lengths. Fermions often have large nuclear spin, which is decoupled from electronic degrees of freedom and leads to a large degree of symmetry and degeneracy in the interaction Hamiltonian. Work done in collaboration with Y.N. Martinez de Escobar, P.G. Mickelson, M. Yan, B.J. DeSalvo, and S.B. Nagel, Rice University.
Review of pseudogaps in strongly interacting Fermi gases
Mueller, Erich J.
A central challenge in modern condensed matter physics is developing the tools for understanding nontrivial yet unordered states of matter. One important idea to emerge in this context is that of a 'pseudogap': the fact that under appropriate circumstances the normal state displays a suppression of the single particle spectral density near the Fermi level, reminiscent of the gaps seen in ordered states of matter. While these concepts arose in a solid state context, they are now being explored in cold gases. This article reviews the current experimental and theoretical understanding of the normal state of strongly interacting Fermi gases, with particular focus on the phenomonology which is traditionally associated with the pseudogap.
Strongly-Interacting Fermi Gases in Reduced Dimensions
superconductivity), nuclear physics (nuclear matter), high - energy physics (effective theories of the strong interactions ), astrophysics (compact stellar objects...strongly- interacting Fermi gases confined in a standing- wave CO2 laser trap. This trap produces a periodic quasi-two-dimensional pancake geometry...predictions of the phase diagram and high temperature superfluidity. Our recent measurements reveal that pairing energy and cloud profiles can be
Effective-range dependence of resonant Fermi gases
Schonenberg, L. M.; Conduit, G. J.
A Fermi gas of cold atoms allows precise control over the dimensionless effective range, kFReff , of the Feshbach resonance. Our pseudopotential formalism allows us to create smooth potentials with effective range, -2 ≤kFReff≤2 , which we use for a variational and diffusion Monte Carlo study of the ground state of a unitary Fermi gas. We report values for the universal constants of ξ =0.388 (1 ) and ζ =0.087 (1 ) , and compute the condensate fraction, momentum distribution, and pair correlations functions. Finally, we show that a gas with kFReff≳1.9 is thermodynamically unstable.
Zero-temperature equation of state of mass-imbalanced resonant Fermi gases.
Braun, Jens; Drut, Joaquín E; Roscher, Dietrich
We calculate the zero-temperature equation of state of mass-imbalanced resonant Fermi gases in an ab initio fashion, by implementing the recent proposal of imaginary-valued mass difference to bypass the sign problem in lattice Monte Carlo calculations. The fully nonperturbative results thus obtained are analytically continued to real mass-imbalance to yield the physical equation of state, providing predictions for upcoming experiments with mass-imbalanced atomic Fermi gases. In addition, we present an exact relation for the rate of change of the equation of state at small mass imbalances, showing that it is fully determined by the energy of the mass-balanced system.
Rotating ideal Fermi gases under a harmonic potential
Li, Yushan
We present a numerical analysis on thermodynamics of a harmonically trapped ideal Fermi gases subjected to either rotating frame or synthetic magnetic field. We discuss the rotation frequency dependency of chemical potential, specific heat, magnetization, particle flow and density profile. Our results demonstrate that the magnetization displays three characteristic regions: mesoscopic fluctuation, de Haas-van Alphen oscillation and Landau diamagnetism. The center and amplitude of oscillation peaks in particle flow in rotating frame exhibit much stronger dependence on rotation frequency than those in synthetic magnetic field.
Rotating ideal Fermi gases under a harmonic potential
Energy Technology Data Exchange (ETDEWEB)
Li, Yushan, E-mail: email@example.com [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Department of Physics, Heze University, Heze 274015 (China)
We present a numerical analysis on thermodynamics of a harmonically trapped ideal Fermi gases subjected to either rotating frame or synthetic magnetic field. We discuss the rotation frequency dependency of chemical potential, specific heat, magnetization, particle flow and density profile. Our results demonstrate that the magnetization displays three characteristic regions: mesoscopic fluctuation, de Haas–van Alphen oscillation and Landau diamagnetism. The center and amplitude of oscillation peaks in particle flow in rotating frame exhibit much stronger dependence on rotation frequency than those in synthetic magnetic field.
Two-dimensional Bose and Fermi gases beyond weak coupling
França, Guilherme; LeClair, André; Squires, Joshua
Using a formalism based on the two-body S-matrix we study two-dimensional Bose and Fermi gases with both attractive and repulsive interactions. Approximate analytic expressions, valid at weak coupling and beyond, are developed and applied to the Berezinskii-Kosterlitz-Thouless (BKT) transition. We successfully recover the correct logarithmic functional form of the critical chemical potential and density for the Bose gas. For fermions, the BKT critical temperature is calculated in BCS and BEC regimes through consideration of Tan's contact.
Atomic physics: Cold gases venture into Flatland
Burnett, Keith
Vortex structures have revealed a lot about the nature of three-dimensional Bose-Einstein condensates. They play an even bigger part in two-dimensional cold atomic gases and drive a fundamentally different phase transition.
Effective-range dependence of two-dimensional Fermi gases
Schonenberg, L. M.; Verpoort, P. C.; Conduit, G. J.
The Feshbach resonance provides precise control over the scattering length and effective range of interactions between ultracold atoms. We propose the ultratransferable pseudopotential to model effective interaction ranges -1.5 ≤kF2Reff2≤0 , where Reff is the effective range and kF is the Fermi wave vector, describing narrow to broad Feshbach resonances. We develop a mean-field treatment and exploit the pseudopotential to perform a variational and diffusion Monte Carlo study of the ground state of the two-dimensional Fermi gas, reporting on the ground-state energy, contact, condensate fraction, momentum distribution, and pair-correlation functions as a function of the effective interaction range across the BEC-BCS crossover. The limit kF2Reff2→-∞ is a gas of bosons with zero binding energy, whereas ln(kFa )→-∞ corresponds to noninteracting bosons with infinite binding energy.
All-optical cooling of Fermi gases via Pauli inhibition of spontaneous emission
Onofrio, Roberto
A technique is proposed to cool Fermi gases to the regime of quantum degeneracy based on the expected inhibition of spontaneous emission due to the Pauli principle. The reduction of the linewidth for spontaneous emission originates a corresponding reduction of the Doppler temperature, which under specific conditions may give rise to a runaway process through which fermions are progressively cooled. The approach requires a combination of a magneto-optical trap as a cooling system and an optical dipole trap to enhance quantum degeneracy. This results in expected Fermi degeneracy factors $T/T_F$ comparable to the lowest values recently achieved, with potential for a direct implementation in optical lattices. The experimental demonstration of this technique should also indirectly provide a macroscopic manifestation of the Pauli exclusion principle at the atomic physics level.
Electron-Atom Collisions in Gases
Kraftmakher, Yaakov
Electron-atom collisions in gases are an aspect of atomic physics. Three experiments in this field employing a thyratron are described: (i) the Ramsauer-Townsend effect, (ii) the excitation and ionization potentials of xenon and (iii) the ion-electron recombination after interrupting the electric discharge.
Dimensional BCS-BEC crossover in ultracold Fermi gases
Energy Technology Data Exchange (ETDEWEB)
Boettcher, Igor
We investigate thermodynamics and phase structure of ultracold Fermi gases, which can be realized and measured in the laboratory with modern trapping techniques. We approach the subject from a both theoretical and experimental perspective. Central to the analysis is the systematic comparison of the BCS-BEC crossover of two-component fermions in both three and two dimensions. A dimensional reduction can be achieved in experiments by means of highly anisotropic traps. The Functional Renormalization Group (FRG) allows for a description of both cases in a unified theoretical framework. In three dimensions we discuss with the FRG the influence of high momentum particles onto the density, extend previous approaches to the Unitary Fermi Gas to reach quantitative precision, and study the breakdown of superfluidity due to an asymmetry in the population of the two fermion components. In this context we also investigate the stability of the Sarma phase. For the two-dimensional system scattering theory in reduced dimension plays an important role. We present both the theoretically as well as experimentally relevant aspects thereof. After a qualitative analysis of the phase diagram and the equation of state in two dimensions with the FRG we describe the experimental determination of the phase diagram of the two-dimensional BCS-BEC crossover in collaboration with the group of S. Jochim at PI Heidelberg.
Quantum kinetic theory of trapped atomic gases
Stoof, H.T.C.
We pesent a general framework in which we can accurately describe the non-equilibrium of trapped atomic gases. This is achieved by deriving a single Fokker-Planck equation for the gas. In this way we are able to discuss not only the dynamics of an interacting gas above and below the critical
Topological superradiant state in Fermi gases with cavity induced spin-orbit coupling
Yu, Dongyang; Pan, Jian-Song; Liu, Xiong-Jun; Zhang, Wei; Yi, Wei
Coherently driven atomic gases inside optical cavities hold great promise for generating rich dynamics and exotic states of matter. It was shown recently that an exotic topological superradiant state exists in a two-component degenerate Fermi gas coupled to a cavity, where local order parameters coexist with global topological invariants. In this work, we characterize in detail various properties of this exotic state, focusing on the feedback interactions between the atoms and the cavity field. In particular, we demonstrate that cavity-induced interband coupling plays a crucial role in inducing the topological phase transition between the conventional and topological superradiant states. We analyze the interesting signatures in the cavity field left by the closing and reopening of the atomic bulk gap across the topological phase boundary and discuss the robustness of the topological superradiant state by investigating the steady-state phase diagram under various conditions. Furthermore, we consider the interaction effect and discuss the interplay between the pairing order in atomic ensembles and the superradiance of the cavity mode. Our work provides many valuable insights into the unique cavity-atom hybrid system under study and is helpful for future experimental exploration of the topological superradiant state.
Finite-range effects in dilute Fermi gases at unitarity
Energy Technology Data Exchange (ETDEWEB)
Simonucci, Stefano [Department of Physics, University of Camerino, via Madonna delle Carceri 9, I-62032 Camerino, Italy, and INFN Sezione Perugia (Italy); Interdisciplinary Laboratory for Computational Science (LISC), FBK-CMM and University of Trento, via Sommarive 18, I-38123 Trento (Italy); Garberoglio, Giovanni [Interdisciplinary Laboratory for Computational Science (LISC), FBK-CMM and University of Trento, via Sommarive 18, I-38123 Trento (Italy); Taioli, Simone [Interdisciplinary Laboratory for Computational Science (LISC), FBK-CMM and University of Trento, via Sommarive 18, I-38123 Trento (Italy); Department of Physics, University of Trento, Via Sommarive 14, I-38123, Trento (Italy)
We develop a theoretical method going beyond the contact-interaction approximation frequently used in mean-field theories of many-fermion systems, based on the low-energy T matrix of the pair potential to rigorously define the effective radius of the interaction. One of the main consequences of our approach is the possibility to investigate finite-density effects, which are outside the range of validity of approximations based on {delta}-like potentials. We apply our method to the calculation of density-dependent properties of an ultracold gas of {sup 6}Li atoms at unitarity, whose two-body interaction potential is calculated using ab initio quantum chemistry methods. We find that density effects will be significant in ultracold gases with densities 1 order of magnitude higher than those attained in current experiments.
Spin-Motion Coupling in Cold Atomic Gases
Koller, A. P.
The interplay between spin and motional degrees of freedom in interacting electron systems has been a long-standing research topic in condensed matter physics. Interactions can modify the behavior of individual electrons and give rise to emergent collective phenomena such as superconductivity and colossal magnetoresistance. Theoretical understanding of non-equilibrium dynamics in interacting fermionic matter is limited, however, and many open questions remain. Ultracold atomic Fermi gases, with precisely controllable parameters, offer an outstanding opportunity to investigate the emergence of collective behavior in out-of-equilibrium settings. In this thesis we will describe how an optical lattice clock operated with neutral Fermionic atoms can be turned into a quantum simulator of charged particles in a strong magnetic field. We will then discuss the counterintuitive notion that weak interactions in a Fermi gas can lead to large scale collective behavior and global correlations. These ideas are being tested experimentally at JILA and the University of Toronto. We also investigate in detail the so-called spin model approximation which is used extensively throughout this thesis.
Repulsive polarons and itinerant ferromagnetism in strongly polarized Fermi gases
DEFF Research Database (Denmark)
Massignan, Pietro; Bruun, Georg
We analyze the properties of a single impurity immersed in a Fermi sea. At positive energy and scattering lengths, we show that the system possesses a well-defined but metastable excitation, the repulsive polaron, and we calculate its energy, quasiparticle residue and effective mass. From a therm...
The explicit expression of the fugacity for weakly interacting Bose and Fermi gases
Dai, Wu-Sheng; Xie, Mi
In this paper, we calculate the explicit expression for the fugacity for two- and three-dimensional weakly interacting Bose and Fermi gases from their equations of state in isochoric and isobaric processes, respectively, based on the mathematical result of the boundary problem of analytic functions—the homogeneous Riemann-Hilbert problem. We also discuss the Bose-Einstein condensation phase transition of three-dimensional hard-sphere Bose gases.
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The influence of the dimensionality of the system on the realization of unconventional Fulde–Ferrell–Larkin–Ovchinnikov pairing in ultra-cold Fermi gases
Ptok, Andrzej
The recent development of experimental techniques in ultracold atomic Fermi gases is extremely helpful in the progress of the realization of the unconventional Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) superfluid phase in quasi-one dimensional systems (Liao et al 2010 Nature 467 567). Due to a Fermi surface nesting, which is enhanced in 1D, the low-dimensional systems are particularly good candidates to find the FFLO phase stable. We investigate the influence of a dimensional crossover (from one dimension (1D) to two dimensions (2D) or three dimensions (3D)) on the stability of the FFLO state in the spin-imbalanced attractive Hubbard model.
Quantum Engineering of Strongly Correlated Matter with Ultracold Fermi Gases
Transport of electron spin, rather than of charge, is being explored as a new way to carry information. Neutrino transport energizes supernova explosions...interaction between an impurity and a fermionic atom using their vacuum scattering length. Treating the pairing of fermions at the mean -field level
Inhomogeneous atomic Bose-Fermi mixtures in cubic lattices.
Cramer, M; Eisert, J; Illuminati, F
We determine the ground state properties of inhomogeneous mixtures of bosons and fermions in cubic lattices and parabolic confining potentials. For finite hopping we determine the domain boundaries between Mott-insulator plateaux and hopping-dominated regions for lattices of arbitrary dimension within mean-field and perturbation theory. The results are compared with a new numerical method that is based on a Gutzwiller variational approach for the bosons and an exact treatment for the fermions. The findings can be applied as a guideline for future experiments with trapped atomic Bose-Fermi mixtures in optical lattices.
Proximity effects in cold gases of multiply charged atoms (Review)
Chikina, I.; Shikin, V.
Possible proximity effects in gases of cold, multiply charged atoms are discussed. Here we deal with rarefied gases with densities nd of multiply charged (Z ≫ 1) atoms at low temperatures in the well-known Thomas-Fermi (TF) approximation, which can be used to evaluate the statistical properties of single atoms. In order to retain the advantages of the TF formalism, which is successful for symmetric problems, the external boundary conditions accounting for the finiteness of the density of atoms (donors), nd ≠ 0, are also symmetrized (using a spherical Wigner-Seitz cell) and formulated in a standard way that conserves the total charge within the cell. The model shows that at zero temperature in a rarefied gas of multiply charged atoms there is an effective long-range interaction Eproxi(nd), the sign of which depends on the properties of the outer shells of individual atoms. The long-range character of the interaction Eproxi is evaluated by comparing it with the properties of the well-known London dispersive attraction ELond(nd) 0 and for the alkali and alkaline-earth elements Eproxi theory through the temperature dependence of the different versions of Eproxi. The anomaly in the thermal proximity effect shows up in the following way: for T ≠ 0 there is no equilibrium solution of TS statistics for single multiply charged atoms in a vacuum when the effect is present. Instability is suppressed in a Wigner-Seitz model under the assumption that there are no electron fluxes through the outer boundary R3 ∝ n-1d of a Wigner-Seitz cell. Eproxi corresponds to the definition of the correlation energy in a gas of interacting particles. This review is written so as to enable comparison of the results of the TF formalism with the standard assumptions of the correlation theory for classical plasmas. The classic example from work on weak solutions (including charged solutions)—the use of semi-impermeable membranes for studies of osmotic pressure—is highly appropriate for
Simulating Chiral Magnetic and Separation Effects with Spin-Orbit Coupled Atomic Gases
Huang, Xu-Guang
The chiral magnetic and chiral separation effects—quantum-anomaly-induced electric current and chiral current along an external magnetic field in parity-odd quark-gluon plasma—have received intense studies in the community of heavy-ion collision physics. We show that analogous effects occur in rotating trapped Fermi gases with Weyl-Zeeman spin-orbit coupling where the rotation plays the role of an external magnetic field. These effects can induce a mass quadrupole in the atomic cloud along the rotation axis which may be tested in future experiments. Our results suggest that the spin-orbit coupled atomic gases are potential simulators of the chiral magnetic and separation effects.
Symplectic Fermi liquid and its realization in cold atomic systems
Ramires, Aline
In this work, we study a system of interacting fermions with large spin and SP(N ) symmetry. We contrast their behavior with the case of SU(N ) symmetry by analyzing the conserved quantities and the dynamics in each case. We also develop the Fermi liquid theory for fermions with SP(N ) symmetry. We find that the effective mass and inverse compressibility are always enhanced in the presence of interactions and that the N dependence of the enhancement is qualitatively different in distinct parameter regimes. The Wilson ratio can be enhanced, indicating that the system can be made closer to a magnetic instability, in contrast to the SU(N ) scenario. We conclude by discussing the experimental routes to SP(N ) symmetry within cold atoms and the exciting possibility of realizing physics in higher dimensions in these systems.
Ultracold Fermi and Bose gases and Spinless Bose Charged Sound Particles
Directory of Open Access Journals (Sweden)
Minasyan V.
Full Text Available We propose a novel approach for investigation of the motion of Bose or Fermi liquid (or gas which consists of decoupled electrons and ions in the uppermost hyperfine state. Hence, we use such a concept as the fluctuation motion of "charged fluid particles" or "charged fluid points" representing a charged longitudinal elastic wave. In turn, this elastic wave is quantized by spinless longitudinal Bose charged sound particles with the rest mass m and charge e 0 . The existence of spinless Bose charged sound particles allows us to present a new model for description of Bose or Fermi liquid via a non-ideal Bose gas of charged sound particles . In this respect, we introduce a new postulation for the superfluid component of Bose or Fermi liquid determined by means of charged sound particles in the condensate, which may explain the results of experiments connected with ultra-cold Fermi gases of spin-polarized hydrogen, 6 Li and 40 K, and such a Bose gas as 87 Rb in the uppermost hyperfine state, where the Bose- Einstein condensation of charged sound particles is realized by tuning the magnetic field.
Three-component topological superfluid in one-dimensional Fermi gases with spin-orbit coupling
Chen, Jie; Hu, Hui; Xianlong, Gao
We theoretically investigate one-dimensional three-component spin-orbit-coupled Fermi gases in the presence of the Zeeman field. By solving the Bogoliubov-de Gennes equations, we obtain the phase diagram at a given chemical potential and order parameter. We show that, with increasing the intensity of the Zeeman field, in addition to undergoing a phase transition from Bardeen-Cooper-Schrieffer (BCS) superfluid to topological superfluid, similar to the two-component system, the three-component system may exhibit some other interesting topological phase transitions. For example, by appropriately adjusting the chemical potential μ, the system can be in a nontrivial topological superfluid in the whole region of the Zeeman field h. It also may initially be a topological superfluid and then translate to a topologically trivial BCS superfluid with increasing the field h. Even more exotically, the system may exhibit a re-entrance behavior, being a topological superfluid at small and large fields but a topologically trivial BCS superfluid in between at a mediate Zeeman field. It can therefore have two regions with zero-energy Majorana fermions. As a consequence of these interesting topological phase transitions, the system of the three-component spin-orbit-coupled Fermi gases in a certain parameter range is more optimizing for the experimental realization of the topological phase due to the smaller magnetic field needed. Thus, a promising candidate for the realization of the topological phase is proposed.
Vortex arrays in neutral trapped Fermi gases through the BCS-BEC crossover
Simonucci, S.; Pieri, P.; Strinati, G. Calvanese
Vortex arrays in type-II superconductors reflect the translational symmetry of an infinite system. There are cases, however, such as ultracold trapped Fermi gases and the crust of neutron stars, where finite-size effects make it complex to account for the geometrical arrangement of vortices. Here, we self-consistently generate these arrays of vortices at zero and finite temperature through a microscopic description of the non-homogeneous superfluid based on a differential equation for the local order parameter, obtained by coarse graining the Bogoliubov-de Gennes (BdG) equations. In this way, the strength of the inter-particle interaction is varied along the BCS-BEC crossover, from largely overlapping Cooper pairs in the Bardeen-Cooper-Schrieffer (BCS) limit to dilute composite bosons in the Bose-Einstein condensed (BEC) limit. Detailed comparison with two landmark experiments on ultracold Fermi gases, aimed at revealing the presence of the superfluid phase, brings out several features that make them relevant for other systems in nature as well.
Physical replicas and the Bose glass in cold atomic gases
Energy Technology Data Exchange (ETDEWEB)
Morrison, S; Kantian, A; Daley, A J; Zoller, P [Institute for Theoretical Physics, University of Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Katzgraber, H G [Theoretische Physik, ETH Zurich, CH-8093 Zuerich (Switzerland); Lewenstein, M [ICAO-Institut de Ciencies Fotoniques, Parc Mediterrani de la Tecnologia, E-08860 Castelldefels, Barcelona (Spain); Buechler, H P [Institute for Theoretical Physics III, University of Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart (Germany)], E-mail: firstname.lastname@example.com
We study cold atomic gases in a disorder potential and analyse the correlations between different systems subjected to the same disorder landscape. Such independent copies with the same disorder landscape are known as replicas. While, in general, these are not accessible experimentally in condensed matter systems, they can be realized using standard tools for controlling cold atomic gases in an optical lattice. Of special interest is the overlap function which represents a natural order parameter for disordered systems and is a correlation function between the atoms of two independent replicas with the same disorder. We demonstrate an efficient measurement scheme for the determination of this disorder-induced correlation function. As an application, we focus on the disordered Bose-Hubbard model and determine the overlap function within the perturbation theory and a numerical analysis. We find that the measurement of the overlap function allows for the identification of the Bose-glass phase in certain parameter regimes.
Magnetic properties of spin-1/2 Fermi gases with ferromagnetic interaction
Wang, Baobao; Qin, Jihong; Guo, Huaiming
We investigate the magnetic properties of spin-1/2 charged Fermi gases with ferromagnetic coupling via mean-field theory, and find the interplay among the paramagnetism, diamagnetism and ferromagnetism. Paramagnetism and diamagnetism compete with each other. When increasing the ferromagnetic coupling the spontaneous magnetization occurs in a weak magnetic field. The critical ferromagnetic coupling constant of the paramagnetic phase to ferromagnetic phase transition increases linearly with the temperature. Both the paramagnetism and diamagnetism increase when the magnetic field increases. It reveals the magnetization density bar M increases firstly as the temperature increases, and then reaches a maximum. Finally the magnetization density bar M decreases smoothly in the high temperature region. The domed shape of the magnetization density bar M variation is different from the behavior of Bose gas with ferromagnetic coupling. We also find the curve of susceptibility follows the Curie-Weiss law, and for a given temperature the susceptibility is directly proportional to the Landé factor.
Resonant scattering and microscopic model of spinless Fermi gases in one-dimensional optical lattices
Cui, Xiaoling
We study the effective Bloch-wave scattering of a spinless Fermi gas in one-dimensional (1D) optical lattices. By tuning the odd-wave scattering length, we find multiple resonances of Bloch waves scattering at the bottom (and the top) of the lowest band, beyond which an attractive (and a repulsive) two-body bound state starts to emerge. These resonances exhibit comparable widths in the deep lattice limit, and the finite interaction range plays an essential role in determining their locations. Based on exact two-body solutions, we construct an effective microscopic model for the low-energy scattering of fermions. The model can reproduce not only the scattering amplitudes of Bloch waves at the lowest-band bottom or top, but also the attractive or repulsive bound states within a reasonably large energy range below or above the band. These results lay the foundation for quantum simulating topological states in cold Fermi gases confined in 1D optical lattices.
Theoretical Approach to the Gauge Invariant Linear Response Theories for Ultracold Fermi Gases with Pseudogap
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Hao Guo
Full Text Available Recent experimental progress allows for exploring some important physical quantities of ultracold Fermi gases, such as the compressibility, spin susceptibility, viscosity, optical conductivity, and spin diffusivity. Theoretically, these quantities can be evaluated from suitable linear response theories. For BCS superfluid, it has been found that the gauge invariant linear response theories can be fully consistent with some stringent consistency constraints. When the theory is generalized to stronger than BCS regime, one may meet serious difficulties to satisfy the gauge invariance conditions. In this paper, we try to construct density and spin linear response theories which are formally gauge invariant for a Fermi gas undergoing BCS-Bose-Einstein Condensation (BEC crossover, especially below the superfluid transition temperature Tc. We adapt a particular t-matrix approach which is close to the G0G formalism to incorporate noncondensed pairing in the normal state. We explicitly show that the fundamental constraints imposed by the Ward identities and Q-limit Ward identity are indeed satisfied.
Low-lying excitation modes of trapped dipolar Fermi gases: From the collisionless to the hydrodynamic regime
Wächtler, Falk; Lima, Aristeu R. P.; Pelster, Axel
By means of the Boltzmann-Vlasov kinetic equation we investigate dynamical properties of a trapped one-component Fermi gas at zero temperature, featuring the anisotropic and long-range dipole-dipole interaction. To this end, we determine an approximate solution by rescaling both space and momentum variables of the equilibrium distribution, thereby obtaining coupled ordinary differential equations for the corresponding scaling parameters. Based on previous results on how the Fermi sphere is deformed in the hydrodynamic regime of a dipolar Fermi gas, we are able to implement the relaxation-time approximation for the collision integral. Then, we proceed by linearizing the equations of motion around the equilibrium in order to study both the frequencies and the damping of the low-lying excitation modes all the way from the collisionless to the hydrodynamic regime. Our theoretical results are expected to be relevant for understanding current experiments with trapped dipolar Fermi gases.
National Aeronautics and Space Administration — Fermi is a powerful space observatory that will open a wide window on the universe. Gamma rays are the highest-energy form of light, and the gamma-ray sky is...
Experimental studies of spin-imbalanced Fermi gases in 2D geometries
Thomas, John
We study the thermodynamics of a quasi-two-dimensional Fermi gas, which is not quite two-dimensional (2D), but far from three dimensional (3D). This system offers opportunities to test predictions that cross interdisciplinary boundaries, such as enhanced superfluid transition temperatures in spin-imbalanced quasi-2D superconductors, and provides important benchmarks for calculations of the phase diagrams. In the experiments, an ultra-cold Fermi gas is confined in an infrared CO2 laser standing-wave, which produces periodic pancake-shaped potential wells, separated by 5.3 μm. To study the thermodynamics, we load an ultra-cold mixture of N1 = 800 spin 1/2 -up and N2 interaction strength and spin imbalance N2/N1. The measured properties are in disagreement with 2D-BCS theory, but can be fit by a 2D-polaron gas model, where each atom is surrounded by a cloud of particle-hole pairs of the opposite spin. However, this model fails to predict a transition to a spin-balanced central region as N2/N1is increased. Supported by the physics divisions of ARO, AFOSR, and NSF and by the Division of Materials Science and Engineering, the Office of Basic Energy Sciences, DOE.
In situ magnetometry for experiments with atomic quantum gases
Krinner, Ludwig; Stewart, Michael; Pazmiño, Arturo; Schneble, Dominik
Precise control of magnetic fields is a frequent challenge encountered in experiments with atomic quantum gases. Here we present a simple method for performing in situ monitoring of magnetic fields that can readily be implemented in any quantum-gas apparatus in which a dedicated field-stabilization approach is not feasible. The method, which works by sampling several Rabi resonances between magnetically field sensitive internal states that are not otherwise used in a given experiment, can be integrated with standard measurement sequences at arbitrary fields. For a condensate of 87Rb atoms, we demonstrate the reconstruction of Gauss-level bias fields with an accuracy of tens of microgauss and with millisecond time resolution. We test the performance of the method using measurements of slow resonant Rabi oscillations on a magnetic-field sensitive transition and give an example for its use in experiments with state-selective optical potentials.
Spontaneous generation of spin-orbit coupling in magnetic dipolar Fermi gases
Sogo, T; M. Urban; Schuck, P.; Miyakawa, T
The stability of an unpolarized two-component dipolar Fermi gas is studied within mean-field theory. Besides the known instability towards spontaneous magnetization with Fermi sphere deformation, another instability towards spontaneous formation of a spin-orbit coupled phase with a Rashba-like spin texture is found. A phase diagram is presented and consequences are briefly discussed.
The pope of physics Enrico Fermi and the birth of the atomic age
Segre, Gino
Enrico Fermi is unquestionably among the greats of the world's physicists, the most famous Italian scientist since Galileo. Called the Pope by his peers, he was regarded as infallible in his instincts and research. His discoveries changed our world; they led to weapons of mass destruction and conversely to life-saving medical interventions. This unassuming man struggled with issues relevant today, such as the threat of nuclear annihilation and the relationship of science to politics. Fleeing Fascism and anti-Semitism, Fermi became a leading figure in America's most secret project: building the atomic bomb. The last physicist who mastered all branches of the discipline, Fermi was a rare mixture of theorist and experimentalist. His rich legacy encompasses key advances in fields as diverse as comic rays, nuclear technology, and early computers. In their revealing book, The Pope of Physics, Gino Segré and Bettina Hoerlin bring this scientific visionary to life. An examination of the human dramas that touched F...
High-temperature atomic superfluidity in lattice Bose-Fermi mixtures.
Illuminati, Fabrizio; Albus, Alexander
We consider atomic Bose-Fermi mixtures in optical lattices and study the superfluidity of fermionic atoms due to s-wave pairing induced by boson-fermion interactions. We prove that the induced fermion-fermion coupling is always attractive if the boson-boson on-site interaction is repulsive, and predict the existence of an enhanced BEC-BCS crossover as the strength of the lattice potential is varied. We show that for direct on-site fermion-fermion repulsion, the induced attraction can give rise to superfluidity via s-wave pairing at striking variance with the case of pure systems of fermionic atoms with direct repulsive interactions.
Fermi polaron-polaritons in charge-tunable atomically thin semiconductors
Sidler, Meinrad; Back, Patrick; Cotlet, Ovidiu; Srivastava, Ajit; Fink, Thomas; Kroner, Martin; Demler, Eugene; Imamoglu, Atac
The dynamics of a mobile quantum impurity in a degenerate Fermi system is a fundamental problem in many-body physics. The interest in this field has been renewed due to recent ground-breaking experiments with ultracold Fermi gases. Optical creation of an exciton or a polariton in a two-dimensional electron system embedded in a microcavity constitutes a new frontier for this field due to an interplay between cavity coupling favouring ultralow-mass polariton formation and exciton-electron interactions leading to polaron or trion formation. Here, we present cavity spectroscopy of gate-tunable monolayer MoSe2 (ref. ) exhibiting strongly bound trion and polaron resonances, as well as non-perturbative coupling to a single microcavity mode. As the electron density is increased, the oscillator strength determined from the polariton splitting is gradually transferred from the higher-energy repulsive exciton-polaron resonance to the lower-energy attractive exciton-polaron state. Simultaneous observation of polariton formation in both attractive and repulsive branches indicates a new regime of polaron physics where the polariton impurity mass can be much smaller than that of the electrons. Our findings shed new light on optical response of semiconductors in the presence of free carriers by identifying the Fermi polaron nature of excitonic resonances and constitute a first step in investigation of a new class of degenerate Bose-Fermi mixtures.
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... COMMISSION DTE ENERGY; Enrico Fermi Atomic Power Plant Unit 1; Exemption From Certain Low-Level Waste Shipment Tracking Requirements In 10 CFR Part 20 Appendix G 1.0 Background DTE Energy (DTE) is the licensee.... DTE is in the process of decommissioning Fermi-1 and radioactive waste shipments from the site are...
Conformal field theory for inhomogeneous one-dimensional quantum systems: the example of non-interacting Fermi gases
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Jérôme Dubail, Jean-Marie Stéphan, Jacopo Viti, Pasquale Calabrese
Full Text Available Conformal field theory (CFT has been extremely successful in describing large-scale universal effects in one-dimensional (1D systems at quantum critical points. Unfortunately, its applicability in condensed matter physics has been limited to situations in which the bulk is uniform because CFT describes low-energy excitations around some energy scale, taken to be constant throughout the system. However, in many experimental contexts, such as quantum gases in trapping potentials and in several out-of-equilibrium situations, systems are strongly inhomogeneous. We show here that the powerful CFT methods can be extended to deal with such 1D situations, providing a few concrete examples for non-interacting Fermi gases. The system's inhomogeneity enters the field theory action through parameters that vary with position; in particular, the metric itself varies, resulting in a CFT in curved space. This approach allows us to derive exact formulas for entanglement entropies which were not known by other means.
In-medium bound-state formation and inhomogeneous condensation in Fermi gases in a hard-wall box
Roscher, Dietrich; Braun, Jens
The formation of bosonic bound states underlies the formation of a superfluid ground state in the many-body phase diagram of ultracold Fermi gases. We study bound-state formation in a spin- and mass-imbalanced ultracold Fermi gas confined in a box with hard-wall boundary conditions. Because of the presence of finite Fermi spheres, the center-of-mass momentum of the potentially formed bound states can be finite, depending on the parameters controlling mass and spin imbalance as well as the coupling strength. We exploit this observation to estimate the potential location of inhomogeneous phases in the many-body phase diagram as a function of spin- and mass imbalance as well as the box size. Our results suggest that a hard-wall box does not alter substantially the many-body phase diagram calculated in the thermodynamic limit. Therefore, such a box may serve as an ideal trap potential to bring experiment and theory closely together and facilitate the search for exotic inhomogeneous ground states.
Properties of ground states of atomic nuclei in self-consistent theory of finite fermi-system
Energy Technology Data Exchange (ETDEWEB)
Sapershtejn, Eh.E.; Khodel' , V.A. (Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Moscow. Inst. Atomnoj Ehnergii)
Ground states of atomic nuclei are described within the framework of the self-consistent theory of finite Fermi systems. The developed approach is compared with the Hartree-Fock method with effective forces.
Mapping the Two-Component Atomic Fermi Gas to the Nuclear Shell-Model
DEFF Research Database (Denmark)
Özen, C.; Zinner, Nikolaj Thomas
of the external potential becomes important. A system of two-species fermionic cold atoms with an attractive zero-range interaction is analogous to a simple model of nucleus in which neutrons and protons interact only through a residual pairing interaction. In this article, we discuss how the problem of a two......-component atomic fermi gas in a tight external trap can be mapped to the nuclear shell model so that readily available many-body techniques in nuclear physics, such as the Shell Model Monte Carlo (SMMC) method, can be directly applied to the study of these systems. We demonstrate an application of the SMMC method...
A Proposal for measuring Anisotropic Shear Viscosity in Unitary Fermi Gases
Samanta, Rickmoy; Trivedi, Sandip P
We present a proposal to measure anisotropic shear viscosity in a strongly interacting, ultra-cold, unitary Fermi gas confined in a harmonic trap. We introduce anisotropy in this setup by strongly confining the gas in one of the directions with relatively weak confinement in the remaining directions. This system has a close resemblance to anisotropic strongly coupled field theories studied recently in the context of gauge-gravity duality. Computations in such theories (which have gravity duals) revealed that some of the viscosity components of the anisotropic shear viscosity tensor can be made much smaller than the entropy density, thus parametrically violating the bound proposed by Kovtun, Son and Starinets (KSS): $\\frac {\\eta} {s} \\geq \\frac{1}{4 \\pi}$. A Boltzmann analysis performed in a system of weakly interacting particles in a linear potential also shows that components of the viscosity tensor can be reduced. Motivated by these exciting results, we propose two hydrodynamic modes in the unitary Fermi ga...
The Kramers problem with accommodative boundary conditions for quantum Fermi gases
Kostikov, A. A.; Latyshev, A. V.; Yushkanov, A. A.
The Kramers problem of isothermal slip of a quantum Fermi gas with Cercignani boundary conditions is solved analytically. The velocity of isothermal slip is obtained as a function of the accommodation coefficient and the reduced chemical potential—the ratio of the chemical potential to the product of Boltzmann's constant and the absolute temperature. The distribution function of the molecules is presented in explicit form.
Competition between pairing and ferromagnetic instabilities in ultracold Fermi gases near Feshbach resonances
DEFF Research Database (Denmark)
Pekker, D; Babadi, M; Sensarma, R
We study the quench dynamics of a two-component ultracold Fermi gas from the weak into the strong interaction regime, where the short time dynamics are governed by the exponential growth rate of unstable collective modes. We obtain an effective interaction that takes into account both Pauli block...... blocking and the energy dependence of the scattering amplitude near a Feshbach resonance. Using this interaction we analyze the competing instabilities towards Stoner ferromagnetism and pairing....
Spontaneous light emission by atomic hydrogen: Fermi's golden rule without cheating
Debierre, V.; Durt, T.; Nicolet, A.; Zolla, F.
Focusing on the 2 p- 1 s transition in atomic hydrogen, we investigate through first order perturbation theory the time evolution of the survival probability of an electron initially taken to be in the excited (2 p) state. We examine both the results yielded by the standard dipole approximation for the coupling between the atom and the electromagnetic field - for which we propose a cutoff-independent regularisation - and those yielded by the exact coupling function. In both cases, Fermi's golden rule is shown to be an excellent approximation for the system at hand: we found its maximal deviation from the exact behaviour of the system to be of order 10-8 /10-7. Our treatment also yields a rigorous prescription for the choice of the optimal cutoff frequency in the dipole approximation. With our cutoff, the predictions of the dipole approximation are almost indistinguishable at all times from the exact dynamics of the system.
Verification of an analytic fit for the vortex core profile in superfluid Fermi gases
Energy Technology Data Exchange (ETDEWEB)
Verhelst, Nick, E-mail: email@example.com [TQC, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen (Belgium); Klimin, Serghei, E-mail: firstname.lastname@example.com [TQC, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen (Belgium); Department of Theoretical Physics, State University of Moldova, Republic of Moldova (Moldova, Republic of); Tempere, Jacques [TQC, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen (Belgium); Lyman Laboratory of Physics, Harvard University (United States)
Highlights: • The vortex profile in an imbalanced Fermi condensate is investigated. • The analytic fit for the vortex profile is compared with numerical simulations. • The analytic fit excellently agrees with numeric results in the BCS-BEC crossover. - Abstract: A characteristic property of superfluidity and -conductivity is the presence of quantized vortices in rotating systems. To study the BEC-BCS crossover the two most common methods are the Bogoliubov-De Gennes theory and the usage of an effective field theory. In order to simplify the calculations for one vortex, it is often assumed that the hyperbolic tangent yields a good approximation for the vortex structure. The combination of a variational vortex structure, together with cylindrical symmetry yields analytic (or numerically simple) expressions. The focus of this article is to investigate to what extent this analytic fit truly reflects the vortex structure throughout the BEC-BCS crossover at finite temperatures. The vortex structure will be determined using the effective field theory presented in [Eur. Phys. Journal B 88, 122 (2015)] and compared to the variational analytic solution. By doing this it is possible to see where these two structures agree, and where they differ. This comparison results in a range of applicability where the hyperbolic tangent will be a good fit for the vortex structure.
Larkin-Ovchinnikov superfluidity in a two-dimensional imbalanced atomic Fermi gas
Toniolo, Umberto; Mulkerin, Brendan; Liu, Xia-Ji; Hu, Hui
We present an extensive study of two-dimensional Larkin-Ovchinnikov (LO) superfluidity in a spin-imbalanced two-component atomic Fermi gas. In the context of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, we explore a wide and generic class of pairing gap functions with explicit spatial dependency. The mean-field theory of such phases is applied through the Bogoliubov-de Gennes equations in which the pairing gap can be determined self-consistently. To systematically explore the configuration space we consider both the canonical and grand canonical ensembles where we control the polarization or chemical potentials of the system, respectively. The mean-field calculations enable us to understand the nature of the phase transitions in the fully paired Bardeen-Cooper-Schrieffer (BCS) state, exotic LO phase, and partially polarized free Fermi gas (NPP). The order of the phase transitions has been examined and, in particular, we find a weak first-order phase transition between the exotic inhomogeneous LO phase and the BCS phase. In comparison to the three-dimensional case, where the phase diagram is dominated by a generic separation phase, we predict a broader parameter space for the spatially inhomogeneous LO phase. By computing the superfluid density of the LO phase at different polarization, we show how the superfluidity of the system is suppressed with increasing spin polarization.
Fermi Level Tuning of ZnO Films Through Supercycled Atomic Layer Deposition
Huang, Ruomeng; Ye, Sheng; Sun, Kai; Kiang, Kian S.; de Groot, C. H. (Kees)
A novel supercycled atomic layer deposition (ALD) process which combines thermal ALD process with in situ O2 plasma treatment is presented in this work to deposit ZnO thin films with highly tunable electrical properties. Both O2 plasma time and the number of thermal ALD cycles in a supercycle can be adjusted to achieve fine tuning of film resistivity and carrier concentration up to six orders of magnitude without extrinsic doping. The concentration of hydrogen defects are believed to play a major role in adjusting the electrical properties of ZnO films. Kelvin probe force microscopy results evidently show the shift of Fermi level in different ZnO films and are well associated with the changing of carrier concentration. This reliable and robust technique reported here clearly points towards the capability of using this method to produce ZnO films with controlled properties in different applications.
Atom chip apparatus for experiments with ultracold rubidium and potassium gases.
Ivory, M K; Ziltz, A R; Fancher, C T; Pyle, A J; Sensharma, A; Chase, B; Field, J P; Garcia, A; Jervis, D; Aubin, S
We present a dual chamber atom chip apparatus for generating ultracold (87)Rb and (39)K atomic gases. The apparatus produces quasi-pure Bose-Einstein condensates of 10(4) (87)Rb atoms in an atom chip trap that features a dimple and good optical access. We have also demonstrated production of ultracold (39)K and subsequent loading into the chip trap. We describe the details of the dual chamber vacuum system, the cooling lasers, the magnetic trap, the multicoil magnetic transport system, the atom chip, and two optical dipole traps. Due in part to the use of light-induced atom desorption, the laser cooling chamber features a sufficiently good vacuum to also support optical dipole trap-based experiments. The apparatus is well suited for studies of atom-surface forces, quantum pumping and transport experiments, atom interferometry, novel chip-based traps, and studies of one-dimensional many-body systems.
Sigature of the universal super Efimov Effect: three-body contact in two dimensional Fermi gases
Yu, Zhenhua; Zhang, Pengfei
A new class of universal ``three-body'' bound states has been recently predicted theoretically for identical fermions interacting at p-wave resonance in two dimensions. This phenomenon is called the super Efimov effect since the binding energies of the states follow a intriguing double exponential scaling. However, experimental resolution of this scaling is expected to meet formidable challenges. In this work, we introduce a new thermodynamic quantity, the three-body contact Cθ, to quantify three-body correlations in a two dimensional gas composed of the resonantly interacting fermions; the contact Cθ is the consequence of the underlying universal super Efimov effect in the many-body context. We show how Cθ affects physical observables such as the radio-frequency spectrum, the momentum distribution and the atom loss rate. Signature of the elusive super Efimov effect in the thermodynamic system can be pinned down by the detection of the three-body contact Cθ via these observables. NSFC Grant No. 11474179.
Coherent versus incoherent dynamics during Bose-Einstein condensation in atomic gases
Stoof, H.T.C.
We review and extend the theory of the dynamics of Bose-Einstein condensation in weakly interacting atomic gases. We present in a unified way both the semiclassical theory as well as the full quantum theory. This is achieved by deriving a Fokker-Planck equation that incorporates both the coherent
Multiple Majorana zero modes in atomic Fermi double wires with spin-orbit coupling
Wang, Liang-Liang; Gong, Ming; Liu, W.-M.
Majorana zero modes, quasiparticles with non-Abelian statistics, have gained increasing interest for their fundamental role as building blocks in topological quantum computation. Previous studies have mainly focused on two well-separated Majorana zero modes, which could form two degenerate states serving as one nonlocal qubit for fault-tolerant quantum memory. However, creating and manipulating multiple Majorana zero modes, which could encode more qubits, remain an ongoing research topic. Here we report that multiple Majorana zero modes can exist in atomic Fermi double wires with spin-orbit coupling and perpendicular Zeeman field. This system belongs to the topological BDI class, thus all the topological superfluids are classified by integer numbers. Especially, diverse topological superfluids can be formed in a trap, where the zero energy modes can be found at the interfaces between different topological superfluids. The structure of these zero energy modes in the trap can be engineered by the trapping potential as well as other system parameters. This system would be a significant step towards utilization of Majorana zero modes in quantum computation.
Coexistence of photonic and atomic Bose-Einstein condensates in ideal atomic gases
Directory of Open Access Journals (Sweden)
N. Boichenko
Full Text Available We have studied conditions of photon Bose-Einstein condensate formation that is in thermodynamic equilibrium with ideal gas of two-level Bose atoms below the degeneracy temperature. Equations describing thermodynamic equilibrium in the system were formulated; critical temperatures and densities of photonic and atomic gas subsystems were obtained analytically. Coexistence conditions of these photonic and atomic Bose-Einstein condensates were found. There was predicted the possibility of an abrupt type of photon condensation in the presence of Bose condensate of ground-state atoms: it was shown that the slightest decrease of the temperature could cause a significant gathering of photons in the condensate. This case could be treated as a simple model of the situation known as "stopped light" in cold atomic gas. We also showed how population inversion of atomic levels can be created by lowering the temperature. The latter situation looks promising for light accumulation in atomic vapor at very low temperatures.
Contribution of electron-atom collisions to the plasma conductivity of noble gases
Rosmej, S.; Reinholz, H.; Röpke, G.
We present an approach which allows the consistent treatment of bound states in the context of dc conductivity in dense partially ionized noble gas plasmas. Besides electron-ion and electron-electron collisions, further collision mechanisms owing to neutral constituents are taken into account. Especially at low temperatures of 104to105 K, electron-atom collisions give a substantial contribution to the relevant correlation functions. We suggest an optical potential for the description of the electron-atom scattering which is applicable for all noble gases. The electron-atom momentum-transfer cross section is in agreement with experimental scattering data. In addition, the influence of the medium is analyzed, the optical potential is advanced including screening effects. The position of the Ramsauer minimum is influenced by the plasma. Alternative approaches for the electron-atom potential are discussed. Good agreement of calculated conductivity with experimental data for noble gas plasmas is obtained.
Influence of nearly resonant light on the scattering length in low-temperature atomic gases
Fedichev, P O; Shlyapnikov, G V; Walraven, J T M
We develop the idea of manipulating the scattering length a in low-temperature atomic gases by using nearly resonant light. As found, if the incident light is close to resonance with one of the bound p levels of electronically excited molecule, then virtual radiative transitions of a pair of interacting atoms to this level can significantly change the value and even reverse the sign of a. The decay of the gas due to photon recoil, resulting from the scattering of light by single atoms, and due to photoassociation can be minimized by selecting the frequency detuning and the Rabi frequency. Our calculations show the feasibility of optical manipulations of trapped Bose condensates through a light-induced change in the mean field interaction between atoms, which is illustrated for ^7Li.
Escape factors for thermionic cathodes in atomic gases in a wide electric field range
Benilov, M. S.; Naidis, G. V.; Petrovic, Z. Lj; Radmilovic-Radjenovic, M.; Stojkovic, A.
An approximate analytical expression is obtained for the escape factors for thermionically emitting cathodes in atomic gases that is uniformly valid at all values of the reduced electric field. This expression is used for evaluation of the escape factors in neon, helium and mercury. An independent evaluation is performed by means of Monte Carlo simulations. The analytical results are in good agreement with the results of Monte Carlo simulations, both for reflecting and non-reflecting cathodes.
Escape factors for thermionic cathodes in atomic gases in a wide electric field range
Energy Technology Data Exchange (ETDEWEB)
Benilov, M S [Departamento de Fisica, Universidade da Madeira, Largo do MunicIpio, 9000 Funchal (Portugal); Naidis, G V [Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya 13/19, Moscow 125412 (Russian Federation); Petrovic, Z Lj [Institute of Physics, POB 68, 11080 Zemun, Belgrade (Serbia); Radmilovic-Radjenovic, M [Institute of Physics, POB 68, 11080 Zemun, Belgrade (Serbia); Stojkovic, A [Institute of Physics, POB 68, 11080 Zemun, Belgrade (Serbia)
An approximate analytical expression is obtained for the escape factors for thermionically emitting cathodes in atomic gases that is uniformly valid at all values of the reduced electric field. This expression is used for evaluation of the escape factors in neon, helium and mercury. An independent evaluation is performed by means of Monte Carlo simulations. The analytical results are in good agreement with the results of Monte Carlo simulations, both for reflecting and non-reflecting cathodes.
Critical temperature of Bose-Einstein condensation in trapped atomic Bose-Fermi mixtures
Energy Technology Data Exchange (ETDEWEB)
Albus, A P [Institut fuer Physik, Universitaet Potsdam, D-14469 Potsdam (Germany); Giorgini, S [Dipartimento di Fisica, Universita di Trento, and Istituto Nazionale per la Fisica della Materia, I-38050 Povo (Italy); Illuminati, F [Dipartimento di Fisica, Universita di Salerno, and Istituto Nazionale per la Fisica della Materia, I-84081 Baronissi (Italy); Viverit, L [Dipartimento di Fisica, Universita di Trento, and Istituto Nazionale per la Fisica della Materia, I-38050 Povo (Italy)
We calculate the shift in the critical temperature of Bose-Einstein condensation for a dilute Bose-Fermi mixture confined by a harmonic potential, to lowest order in both the Bose-Bose and Bose-Fermi coupling constants. The relative importance of the effect on the critical temperature of the boson-boson and boson-fermion interactions is investigated as a function of the parameters of the mixture. The possible relevance of the shift of the transition temperature in current experiments on trapped Bose-Fermi mixtures is discussed. (letter to the editor)
Coherent and spontaneous Rayleigh-Brillouin scattering in atomic and molecular gases and gas mixtures
Vieitez, MO; van Duijn; Ubachs, W.; Witschas, B.; Meijer, A.; Wijn, De, JR; Dam, NJ Nico; Water, van de, W Willem
We study Rayleigh-Brillouin scattering in gases of N2, O2, and SF6 molecules, Kr atoms, and He-Xe and He-CO2 mixtures at pressures ranging from 1 to 3 bar and using two different experimental setups. In one setup, we measure spectra of light scattered by thermal density fluctuations (spontaneous Rayleigh-Brillouin scattering); in the second setup density waves are induced in the overlap region of two counterpropagating laser beams (coherent Rayleigh-Brillouin scattering).We compare measured s...
Information and backaction due to phase contrast imaging measurements of cold atomic gases: beyond Gaussian states
Ilo-Okeke, Ebubechukwu O
We further examine a theory of phase contrast imaging (PCI) of cold atomic gases, first introduced by us in Phys. Rev. Lett. {\\bf 112}, 233602 (2014). We model the PCI measurement by directly calculating the entangled state between the light and the atoms due to the ac Stark shift, which induces a conditional phase shift on the light depending upon the atomic state. By interfering the light that passes through the BEC with the original light, one can obtain information of the atomic state at a single shot level. We derive an exact expression for a measurement operator that embodies the information obtained from PCI, as well as the back-action on the atomic state. By the use of exact expressions for the measurement process, we go beyond the continuous variables approximation such that the non-Gaussian regime can be accessed for both the measured state and the post-measurement state. Features such as the photon probability density, signal, signal variance, Fisher information, error of the measurement, and the b...
Indian Academy of Sciences (India)
IAS Admin
acknowledged leader, Fermi was 'the Pope'. His finest achievements in the Rome period were .... to work on the atomic bomb project, under the leadership of. Oppenheimer. After the success of the project and .... Two more gems of his pedagogical skills deserve mention. The first is a book on 'Thermodynamics' based on ...
Phase space methods for degenerate quantum gases
Dalton, Bryan J; Barnett, Stephen M
Recent experimental progress has enabled cold atomic gases to be studied at nano-kelvin temperatures, creating new states of matter where quantum degeneracy occurs - Bose-Einstein condensates and degenerate Fermi gases. Such quantum states are of macroscopic dimensions. This book presents the phase space theory approach for treating the physics of degenerate quantum gases, an approach already widely used in quantum optics. However, degenerate quantum gases involve massive bosonic and fermionic atoms, not massless photons. The book begins with a review of Fock states for systems of identical atoms, where large numbers of atoms occupy the various single particle states or modes. First, separate modes are considered, and here the quantum density operator is represented by a phase space distribution function of phase space variables which replace mode annihilation, creation operators, the dynamical equation for the density operator determines a Fokker-Planck equation for the distribution function, and measurable...
SpectraPlot.com: Integrated spectroscopic modeling of atomic and molecular gases
Goldenstein, Christopher S.; Miller, Victor A.; Mitchell Spearrin, R.; Strand, Christopher L.
SpectraPlot is a web-based application for simulating spectra of atomic and molecular gases. At the time this manuscript was written, SpectraPlot consisted of four primary tools for calculating: (1) atomic and molecular absorption spectra, (2) atomic and molecular emission spectra, (3) transition linestrengths, and (4) blackbody emission spectra. These tools currently employ the NIST ASD, HITRAN2012, and HITEMP2010 databases to perform line-by-line simulations of spectra. SpectraPlot employs a modular, integrated architecture, enabling multiple simulations across multiple databases and/or thermodynamic conditions to be visualized in an interactive plot window. The primary objective of this paper is to describe the architecture and spectroscopic models employed by SpectraPlot in order to provide its users with the knowledge required to understand the capabilities and limitations of simulations performed using SpectraPlot. Further, this manuscript discusses the accuracy of several underlying approximations used to decrease computational time, in particular, the use of far-wing cutoff criteria.
Measuring laser carrier-envelope-phase effects in the noble gases with an atomic hydrogen calibration standard
Khurmi, Champak; Wallace, W. C.; Sainadh U, Satya; Ivanov, I. A.; Kheifets, A. S.; Tong, X. M.; Litvinyuk, I. V.; Sang, R. T.; Kielpinski, D.
We present accurate measurements of carrier-envelope-phase effects on ionization of the noble gases with few-cycle laser pulses. The experimental apparatus is calibrated by using atomic hydrogen data to remove any systematic offsets and thereby obtain accurate CEP data on other generally used noble gases such as Ar, Kr, and Xe. Experimental results for H are well supported by exact time-dependent Schrödinger equation theoretical simulations; however, significant differences are observed in the case of the noble gases.
Coherent and spontaneous Rayleigh-Brillouin scattering in atomic and molecular gases and gas mixtures
Vieitez, M. O.; van Duijn, E. J.; Ubachs, W.; Witschas, B.; Meijer, A.; de Wijn, A. S.; Dam, N. J.; van de Water, W.
We study Rayleigh-Brillouin scattering in gases of N2, O2, and SF6 molecules, Kr atoms, and He-Xe and He-CO2 mixtures at pressures ranging from 1 to 3 bar and using two different experimental setups. In one setup, we measure spectra of light scattered by thermal density fluctuations (spontaneous Rayleigh-Brillouin scattering); in the second setup density waves are induced in the overlap region of two counterpropagating laser beams (coherent Rayleigh-Brillouin scattering). We compare measured spectra to the Tenti models and to a recent model for mixtures. We find new values of the bulk viscosity, which is a parameter in line-shape models that allows for internal degrees of freedom. Both experiments agree on the value of the bulk viscosity. Our results indicate a need for new line-shape models for mixtures of molecules with internal degrees of freedom.
Quantum spin dynamics of mode-squeezed Luttinger liquids in two-component atomic gases.
Widera, Artur; Trotzky, Stefan; Cheinet, Patrick; Fölling, Simon; Gerbier, Fabrice; Bloch, Immanuel; Gritsev, Vladimir; Lukin, Mikhail D; Demler, Eugene
We report on the observation of many-body spin dynamics of interacting, one-dimensional (1D) ultracold bosonic gases with two spin states. By controlling the nonlinear atomic interactions close to a Feshbach resonance we are able to induce a phase diffusive many-body spin dynamics of the relative phase between the two components. We monitor this dynamical evolution by Ramsey interferometry, supplemented by a novel, many-body echo technique, which unveils the role of quantum fluctuations in 1D. We find that the time evolution of the system is well described by a Luttinger liquid initially prepared in a multimode squeezed state. Our approach allows us to probe the nonequilibrium evolution of one-dimensional many-body quantum systems.
On the density profile in Fourier space of harmonically confined ideal quantum gases in d dimensions
Bencheikh, K.; Nieto, L. M.
Closed-form analytical expressions and asymptotic results are obtained for the density distribution in Fourier space of harmonically trapped fermion gases at zero and nonzero temperatures in d dimensions. The result is applied to weakly interacting Fermi gases and to the elastic scattering from atomic nuclei. The Fourier transform of the momentum density for a d-dimensional harmonic confinement is also found.
Goldstone mode and pair-breaking excitations in atomic Fermi superfluids
Hoinka, Sascha; Dyke, Paul; Lingham, Marcus G.; Kinnunen, Jami J.; Bruun, Georg M.; Vale, Chris J.
Spontaneous symmetry breaking is a central paradigm of elementary particle physics, magnetism, superfluidity and superconductivity. According to Goldstone's theorem, phase transitions that break continuous symmetries lead to the existence of gapless excitations in the long-wavelength limit. These Goldstone modes can become the dominant low-energy excitation, showing that symmetry breaking has a profound impact on the physical properties of matter. Here, we present a comprehensive study of the elementary excitations in a homogeneous strongly interacting Fermi gas through the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a Bose-Einstein condensate (BEC) of molecules using two-photon Bragg spectroscopy. The spectra exhibit a discrete Goldstone mode, associated with the broken-symmetry superfluid phase, as well as pair-breaking single-particle excitations. Our techniques yield a direct determination of the superfluid pairing gap and speed of sound in close agreement with strong-coupling theories.
Signature of the universal super Efimov effect: Three-body contact in two-dimensional Fermi gases
Zhang, Pengfei; Yu, Zhenhua
A class of universal "three-body" bound states has been recently predicted theoretically for identical fermions interacting at p -wave resonance in two dimensions. This phenomenon is called the super Efimov effect since the binding energies of the states follow a intriguing double exponential scaling. However, experimental resolution of this scaling is expected to meet formidable challenges. In this work, we introduce a thermodynamic quantity, the three-body contact Cθ, to quantify three-body correlations in a two-dimensional gas composed of the resonantly interacting fermions; the contact Cθ is the consequence of the underlying universal super Efimov effect in the many-body context. We show how Cθ affects physical observables such as the radio-frequency spectrum, the momentum distribution, and the atom loss rate. The signature of the elusive super Efimov effect can be pinned down by the detection of the three-body contact Cθ via these observables in the many-body system.
Progress towards a Fermi Gas Microscope
Gersdorf, Thomas; Ramasesh, Vinay; Inoue, Takuma; Okan, Melih; Reens, David; Goldstein, Jordan; Bakr, Waseem; Zwierlein, Martin
Attractively interacting degenerate Fermi gases near a Feshbach resonance have been used to realize the BEC-BCS crossover, while repulsive gases in optical lattices are expected to shed light on the physics of high-temperature superconductors. Local probes of these atomic systems should reveal microscopic correlations in such strongly interacting systems that cannot be directly extracted from bulk measurements. With the advent of quantum gas microscopy, the potential of such local probes has been demonstrated in bosonic gases. We are developing an experimental apparatus that combines quantum gas microscopy techniques with ultracold fermions in optical lattices to simulate strongly-correlated electronic systems. Our apparatus is designed to create degenerate gases of fermionic lithium and potassium as well as bosonic sodium. The gases will be loaded into a single layer of an optical lattice and imaged with a sub-micron resolution optical system capable of resolving individual sites. Our system opens the door to microscopic studies of phases that appear in the Fermi-Hubbard model including fermionic Mott insulators, antiferromagnets and d-wave superfluids, as well as topological phases that arise in the presence of synthetic gauge fields.
Emission of fast hydrogen atoms at a plasma–solid interface in a low density plasma containing noble gases
Marchuk, O.; Brandt, C.; Pospieszczyk, A.; Reinhart, M.; Brezinsek, S.; Unterberg, B.; Dickheuer, S.
The source of the broad radiation of fast hydrogen atoms in plasmas containing noble gases remains one of the most discussed problems relating to plasma–solid interface. In this paper, we present a detailed study of Balmer lines emission generated by fast hydrogen and deuterium atoms in an energy range between 40 and 300 eV in a linear magnetised plasma. The experiments were performed in gas mixtures containing hydrogen or deuterium and one of the noble gases (He, Ne, Ar, Kr or Xe). In the low-pressure regime (0.01–0.1 Pa) of plasma operation emission is detected by using high spectral and spatial resolution spectrometers at different lines-of-sight for different target materials (C, Fe, Rh, Pd, Ag and W). We observed the spatial evolution for H α , H β and H γ lines with a resolution of 50 μm in front of the targets, proving that emission is induced by reflected atoms only. The strongest radiation of fast atoms was observed in the case of Ar–D or Ar–H discharges. It is a factor of five less in Kr–D plasma and an order of magnitude less in other rare gas mixture plasmas. First, the present work shows that the maximum of emission is achieved for the kinetic energy of 70–120 eV/amu of fast atoms. Second, the emission profile depends on the target material as well as surface characteristics such as the particle reflection, e.g. angular and energy distribution, and the photon reflectivity. Finally, the source of emission of fast atoms is narrowed down to two processes: excitation caused by collisions with noble gas atoms in the ground state, and excitation transfer between the metastable levels of argon and the excited levels of hydrogen or deuterium.
Strong enhancement of Penning ionization for asymmetric atom pairs in cold Rydberg gases: the Tom and Jerry effect
Efimov, D K
We consider Penning ionization of Rydberg atom pairs as an Auger-type process induced by the dipole-dipole interaction and employ semiclassical formulae for dipole transitions to calculate the autoionization width as a function of the principal quantum numbers, n d, n i, of both atoms. While for symmetric atom pairs with the well-known increase of the autoionization width with increasing n 0 is obtained, the result for asymmetric pairs is counterintuitive - for a fixed n i of the ionizing atom of the pair, the autoionization width strongly increases with decreasing n d of the de-excited atom. For H Rydberg atoms this increase reaches two orders of magnitude at the maximum of the n d dependence, and the same type of counterintuitive behavior is exhibited also by Na, Rb and Cs atoms. This is a purely quantum-mechanical effect, which points towards existence of optimal (we call them \\'Tom\\' and \\'Jerry\\' for \\'big\\' and \\'small\\') pairs of Rydberg atoms with respect to autoionization efficiency. Building on the model of population redistribution in cold Rydberg gases proposed in [1], we demonstrate that population evolution following the initial laser excitation of Rydberg atoms in state n 0 would eventually lead to the formation of such Tom-Jerry pairs with which feature autoionization widths that are enhanced by several orders of magnitude compared to that of two atoms in the initial laser-excited state n 0. We also show that in the high-density regime of cold Rydberg gas experiments the ionization rate of Tom-Jerry pairs can be substantially larger than the blackbody radiation-induced photoionization rate. © 2016 IOP Publishing Ltd.
Energy Technology Data Exchange (ETDEWEB)
Erika Bailey
The Enrico Fermi Atomic Power Plant, Unit 1 (Fermi 1) was a fast breeder reactor design that was cooled by sodium and operated at essentially atmospheric pressure. On May 10, 1963, the Atomic Energy Commission (AEC) granted an operating license, DPR-9, to the Power Reactor Development Company (PRDC), a consortium specifically formed to own and operate a nuclear reactor at the Fermi 1 site. The reactor was designed for a maximum capability of 430 megawatts (MW); however, the maximum reactor power with the first core loading (Core A) was 200 MW. The primary system was filled with sodium in December 1960 and criticality was achieved in August 1963.
understanding is the experimental verification of a new model of light-induced loss spectra, employing continuum- dressed basis states, which agrees in...verification of a new model of light-induced loss spectra, employing continuum- dressed basis states, which agrees in shape and magnitude with all of our...loss measurements for both broad and narrow resonances. Using this model, we predict the trade -off between tunability and loss for the broad resonance
Towards Quantum Turbulence in Cold Atomic Fermionic Superfluids
Bulgac, Aurel; Wlazłowski, Gabriel
Fermionic superfluids provide a new realization of quantum turbulence, accessible to both experiment and theory, yet relevant to both cold atoms and nuclear astrophysics. In particular, the strongly interacting Fermi gas realized in cold-atom experiments is closely related to dilute neutron matter in the neutron star crust. Unlike the liquid superfluids 4He (bosons) and 3He (fermions), where quantum turbulence has been studied in laboratory for decades, quantum gases, and in particular superfluid Fermi gases stand apart for a number of reasons. Fermi gases admit a rather reliable microscopic description based on density functional theory which describes both static and dynamical phenomena. Cold atom experiments demonstrate exquisite control over particle number, spin polarization, density, temperature, and interacting strength. Topological defects such as domain walls and quantized vortices, which lie at the heart of quantum turbulence, can be created and manipulated with time-dependent external potentials, a...
Measurement of the diffusion coefficient of oriented Na atoms in different buffer gases
Energy Technology Data Exchange (ETDEWEB)
Bicchi, P. (Siena Univ. (Italy). Ist. di Fisica); Moi, L.; Savino, P.; Zambon, B. (Consiglio Nazionale delle Ricerche, Pisa (Italy). Lab. di Fisica Atomica e Moleculare)
The authors report the measurements of the diffusion coefficients of Na in different buffer gases obtained through the study of the optical activity of Na vapour oriented by laser light. The reliability of this method is analyzed in the different physical situations to which the different buffer gases give rise. The accuracy of the method, in all cases in which extremely short relaxation processes are absent, is confirmed either by the comparison among the diffusion coefficient values here measured and those present in the literature obtained with different techniques, or by the analysis of the polarization distribution in steady conditions, which results to be in good agreement with the theoretical forecasts.
Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases
Directory of Open Access Journals (Sweden)
X. H. Liu
Full Text Available We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.
Probing and Manipulating Ultracold Fermi Superfluids
Jiang, Lei
Ultracold Fermi gas is an exciting field benefiting from atomic physics, optical physics and condensed matter physics. It covers many aspects of quantum mechanics. Here I introduce some of my work during my graduate study. We proposed an optical spectroscopic method based on electromagnetically-induced transparency (EIT) as a generic probing tool that provides valuable insights into the nature of Fermi paring in ultracold Fermi gases of two hyperfine states. This technique has the capability of allowing spectroscopic response to be determined in a nearly non-destructive manner and the whole spectrum may be obtained by scanning the probe laser frequency faster than the lifetime of the sample without re-preparing the atomic sample repeatedly. Both quasiparticle picture and pseudogap picture are constructed to facilitate the physical explanation of the pairing signature in the EIT spectra. Motivated by the prospect of realizing a Fermi gas of 40K atoms with a synthetic non-Abelian gauge field, we investigated theoretically BEC-HCS crossover physics in the presence of a Rashba spin-orbit coupling in a system of two-component Fermi gas with and without a Zeeman field that breaks the population balance. A new bound state (Rashba pair) emerges because of the spin-orbit interaction. We studied the properties of Rashba pairs using a standard pair fluctuation theory. As the two-fold spin degeneracy is lifted by spin-orbit interaction, bound pairs with mixed singlet and triplet pairings (referred to as rashbons) emerge, leading to an anisotropic superfluid. We discussed in detail the experimental signatures for observing the condensation of Rashba pairs by calculating various physical observables which characterize the properties of the system and can be measured in experiment. The role of impurities as experimental probes in the detection of quantum material properties is well appreciated. Here we studied the effect of a single classical impurity in trapped ultracold Fermi
Above-threshold ionization of noble gases in elliptically polarized fields: Effects of atomic polarization on photoelectron angular distributions
Wang, YanLan; Yu, ShaoGang; Lai, XuanYang; Liu, XiaoJun; Chen, Jing
We theoretically investigate the atomic polarization effect on photoelectron angular distributions (PADs) in above-threshold ionization of noble gases with elliptically polarized laser fields at wavelength of 800 nm, ellipticity of 0.25, and intensity of 1.5 ×1014W/cm2 . Simulations based on a semiclassical model that includes both the ionic Coulomb potential and the atomic polarization effect show surprisingly little difference between PADs for Ar, Kr, and Xe, which is in good agreement with recent experimental observations. Our calculations reveal that the atomic polarization effect increases the distance of the tunnel exit point of the photoelectron to the parent ion and weakens the strength of the interaction between the parent ion and the photoelectron on its subsequent classical propagation. As a result, the forward-scattering electrons which contribute to the main lobes in PADs are substantially suppressed. Our results indicate that the insensitivity of PADs for Ar, Kr, and Xe may be closely related to the influence of the atomic polarization effect on the photoelectron dynamics in the strong laser field.
Engineering the Dynamics of Effective Spin-Chain Models for Strongly Interacting Atomic Gases
DEFF Research Database (Denmark)
Volosniev, A. G.; Petrosyan, D.; Valiente, M.
We consider a one-dimensional gas of cold atoms with strong contact interactions and construct an effective spin-chain Hamiltonian for a two-component system. The resulting Heisenberg spin model can be engineered by manipulating the shape of the external confining potential of the atomic gas. We...... find that bosonic atoms offer more flexibility for tuning independently the parameters of the spin Hamiltonian through interatomic (intra-species) interaction which is absent for fermions due to the Pauli exclusion principle. Our formalism can have important implications for control and manipulation...
Velocity-changing collisional effects in nonlinear atomic spectroscopy and photon echo decay in gases
Herman, R. M.
A general theory of atomic dipole coherence under the influence of collisional phase changes, inelastic effects and optically active atom velocity changes, including those due to anisotropic interactions is presented. Velocity change effects are obtained in closed form. Line shapes appear as convolutions of standard pressure broadening contours with velocity-change contours. Width and shift parameters for the He-broadened Na D lines at 2 m bar pressure, 380 K are calculated, as are He-induced photon echo decay rates for these lines. Overall agreement with xperiment is reasonably good.
Atomic data for integrated tokamak modelling – Fermi-shuttle type ionization as a possible source of high energy electrons
Directory of Open Access Journals (Sweden)
Tőkési K.
Full Text Available The ionization of Ar by 15 keV N+ ion is studied theoretically. The energy distributions of the ejected electrons as a function of the scattering angle were calculated using the classical trajectory Monte Carlo method. We identify the signature of the Fermi-shuttle type ionization in the double differential cross sections which should be a possible source of the high energy electrons in the plasma. Our classical calculation also describes the previously measured data with high accuracy.
Quantum gases finite temperature and non-equilibrium dynamics
Szymanska, Marzena; Davis, Matthew; Gardiner, Simon
The 1995 observation of Bose-Einstein condensation in dilute atomic vapours spawned the field of ultracold, degenerate quantum gases. Unprecedented developments in experimental design and precision control have led to quantum gases becoming the preferred playground for designer quantum many-body systems. This self-contained volume provides a broad overview of the principal theoretical techniques applied to non-equilibrium and finite temperature quantum gases. Covering Bose-Einstein condensates, degenerate Fermi gases, and the more recently realised exciton-polariton condensates, it fills a gap by linking between different methods with origins in condensed matter physics, quantum field theory, quantum optics, atomic physics, and statistical mechanics. Thematically organised chapters on different methodologies, contributed by key researchers using a unified notation, provide the first integrated view of the relative merits of individual approaches, aided by pertinent introductory chapters and the guidance of ed...
Many-body effects in Bose-Einstein condensates of dilute atomic gases
Esry, Brett Daniel
The recent experimental achievement of Bose-Einstein condensation in a dilute alkali gas has spurred a great deal of interest among physicists from many fields. Dilute atomic gas experiments are particularly attractive, compared to experiments on the closely related phenomena of superfluidity and superconductivity, because a dilute gas is a weakly interacting system which is far more amenable to theoretical description. Experimentally, dilute gas experiments are advantageous because relatively straightforward and convenient diagnostics exist, using laser excitation of atomic transitions. As a result, dilute atomic gas experiments can be more completely understood using first principles theoretical treatments. I have adapted the Hartree-Fock, random phase, and configuration interaction approximations to describe systems of interacting bosons, and have shown that such systems can be treated accurately and efficiently within a particle number conserving approximation. In fact, the resulting approximations are remarkably similar to those made in the standard Bogoliubov approach and lead to largely the same equations. A key conclusion is that a system of interacting bosons can be treated in a manner analogous to that used to describe the electronic states of atoms. The hope is that the knowledge and intuition that have been gained from the extensive study of the atomic structure problem will ultimately lead to a deeper understanding of the quantum mechanical states of interacting, trapped atoms. In the course of this work, several phenomena are studied using both the Hartree-Fock approximation and the random phase approximation. The resulting analysis of the stability criteria for single and double condensates improves on results available in the literature in both cases. The double condensate ground state is explored for various hyperfine and isotopic combinations of rubidium in fully three-dimensional configurations for realistic numbers of atoms. Random phase
Effective atomic numbers, electron densities, and tissue equivalence of some gases and mixtures for dosimetry of radiation detectors
Directory of Open Access Journals (Sweden)
Singh Vishwanath P.
Full Text Available Total mass attenuation coefficients, µm, effective atomic number, Zeff, and effective electron density, Neff, of different gases - carbon dioxide, methane, acetylene, propane, butane, and pentane used in radiation detectors, have been calculated for the photon energy of 1 keV to 100 GeV. Each gas has constant Zeff values between 0.10 to 10 MeV photon energies; however, these values are way far away from ICRU tissue. Carbon dioxide gas shows the closest tissue equivalence in the entire photon energy spectrum. Relative tissue equivalences of the mixtures of gases with respect to ICRU tissue are in the range of 0.998-1.041 for air, argon (4.5% + methane (95.5%, argon (0.5% + carbon dioxide (99.5%, and nitrogen (5% + methane (7% + carbon dioxide (88%. The gas composition of xenon (0.5% + carbon dioxide (99.5% shows 1.605 times higher tissue equivalence compared to the ICRU tissue. The investigated photon interaction parameters are useful for exposure and energy absorption buildup factors calculation and design, and fabrication of gaseous detectors for ambient radiation measurement by the Geiger-Muller detector, ionization chambers and proportional counters.
Superfluid Fermi atomic gas as a quantum simulator for the study of the neutron-star equation of state in the low-density region
van Wyk, Pieter; Tajima, Hiroyuki; Inotani, Daisuke; Ohnishi, Akira; Ohashi, Yoji
We propose a theoretical idea to use an ultracold Fermi gas as a quantum simulator for the study of the low-density region of a neutron-star interior. Our idea is different from the standard quantum simulator that heads for perfect replication of another system, such as the Hubbard model discussed in high-Tc cuprates. Instead, we use the similarity between two systems and theoretically make up for the difference between them. That is, (1) we first show that the strong-coupling theory developed by Nozières and Schmitt-Rink (NSR) can quantitatively explain the recent experiment on the equation of state (EoS) in a 6Li superfluid Fermi gas in the BCS (Bardeen-Cooper-Schrieffer) unitary limit far below the superfluid phase-transition temperature Tc. This region is considered to be very similar to the low-density region (crust regime) of a neutron star (where a nearly unitary s -wave neutron superfluid is expected). (2) We then theoretically compensate the difference that, while the effective range reff is negligibly small in a superfluid 6Li Fermi gas, it cannot be ignored (reff=2.7 fm) in a neutron star, by extending the NSR theory to include effects of reff. The calculated EoS when reff=2.7 fm is shown to agree well with the previous neutron-star EoS in the low-density region predicted in nuclear physics. Our idea indicates that an ultracold atomic gas may more flexibly be used as a quantum simulator for the study of other complicated quantum many-body systems, when we use not only the experimental high tunability, but also the recent theoretical development in this field. Since it is difficult to directly observe a neutron-star interior, our idea would provide a useful approach to the exploration for this mysterious astronomical object.
Interfaces between Bose-Einstein and Tonks-Girardeau atomic gases
Filatrella, Giovanni; Malomed, Boris A.
We consider one-dimensional mixtures of an atomic Bose-Einstein condensate (BEC) and Tonks- Giradeau (TG) gas. The mixture is modeled by a coupled system of the Gross-Pitaevskii equation for the BEC and the quintic nonlinear Schroedinger equation for the TG component. An immiscibility condition for the binary system is derived in a general form. Under this condition, three types of BEC-TG interfaces are considered: domain walls (DWs) separating the two components; bubble-drops (BDs), in the f...
Metastability and coherence of repulsive polarons in a strongly interacting Fermi mixture
DEFF Research Database (Denmark)
Kohstall, Cristoph; Zaccanti, Mattheo; Jag, Matthias
Ultracold Fermi gases with tunable interactions provide a test bed for exploring the many-body physics of strongly interacting quantum systems1, 2, 3, 4. Over the past decade, experiments have investigated many intriguing phenomena, and precise measurements of ground-state properties have provided...... implies the existence of a weakly bound molecular state, which makes the system intrinsically unstable against decay. Here we use radio-frequency spectroscopy to measure the complete excitation spectrum of fermionic 40K impurities resonantly interacting with a Fermi sea of 6Li atoms. In particular, we...
Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving.
Li, Jiaming; de Melo, Leonardo F; Luo, Le
We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs the anharmonicity of the ODT, in which the hotter atoms at the edge of the trap feel the anharmonic components of the trapping potential, while the colder atoms in the center of the trap feel the harmonic one. By modulating the trap depth with frequencies that are resonant with the anharmonic components, we selectively excite the hotter atoms out of the trap while keeping the colder atoms in the trap, generating parametric cooling. This experimental protocol starts with a magneto-optical trap (MOT) that is loaded by a Zeeman slower. The precooled atoms in the MOT are then transferred to an ODT, and a bias magnetic field is applied to create an interacting Fermi gas. We then lower the trapping potential to prepare a cold Fermi gas near the degenerate temperature. After that, we sweep the magnetic field to the noninteracting regime of the Fermi gas, in which the parametric cooling can be manifested by modulating the intensity of the optical trapping beams. We find that the parametric cooling effect strongly depends on the modulation frequencies and amplitudes. With the optimized frequency and amplitude, we measure the dependence of the cloud energy on the modulation time. We observe that the cloud energy is changed in an anisotropic way, where the energy of the axial direction is significantly reduced by parametric driving. The cooling effect is limited to the axial direction because the dominant anharmonicity of the crossed-beam ODT is along the axial direction. Finally, we propose to extend this protocol for the trapping potentials of large anharmonicity in all directions, which provides a promising scheme for cooling quantum gases using external driving.
On the electronic and magnetic properties of nanostructures, solids and cold atomic gases
Sau, Jay Deep
technique to determine the level alignment and gaps of a molecule in the neighborhood of a substrate. We then test our method by quantitatively comparing the results of this method applied to the C 60 molecule on Au and Ag substrates to experimental scanning tunneling spectroscopy results on these systems. (6) In chapter six we move our focus to bulk systems and use a combination of density functional theory and empirical pseudopotential methods to study the transport properties of Ge-Sn alloy systems. Using the empirical pseudopotential method we find a combination of strain and alloying that turns Ge-Sn into a direct gap semiconductor with low electron and hole masses. The low effective masses implies an increased carrier mobility for the alloy. Using density functional theory calculations we calculate the effect of alloy scattering from Sn in Ge and show that even after taking into account substitutional disorder from alloy scattering Ge-Sn alloys are expected to exhibit higher mobilities than Ge. (7) In the final chapter we apply the combination of a model Hamiltonian and a computational solution of mean field equations that we have been applying to solid state systems to understand and predict the properties of ultra-cold spinor Bose Eintein Condensates. In this study we study the effect of how dipole-dipole interactions between spin-1 Rubidium atoms can directly affect the dynamics of quantum noise induced domain formation and predict ways to directly observe the dipole-dipole interactions between 87Rb.
EDITORIAL: Cold Quantum GasesEditorial: Cold Quantum Gases
Vassen, W.; Hemmerich, A.; Arimondo, E.
This Special Issue of Journal of Optics B: Quantum and Semiclassical Optics brings together the contributions of various researchers working on theoretical and experimental aspects of cold quantum gases. Different aspects of atom optics, matter wave interferometry, laser manipulation of atoms and molecules, and production of very cold and degenerate gases are presented. The variety of subjects demonstrates the steadily expanding role associated with this research area. The topics discussed in this issue, extending from basic physics to applications of atom optics and of cold atomic samples, include: bulletBose--Einstein condensation bulletFermi degenerate gases bulletCharacterization and manipulation of quantum gases bulletCoherent and nonlinear cold matter wave optics bulletNew schemes for laser cooling bulletCoherent cold molecular gases bulletUltra-precise atomic clocks bulletApplications of cold quantum gases to metrology and spectroscopy bulletApplications of cold quantum gases to quantum computing bulletNanoprobes and nanolithography. This special issue is published in connection with the 7th International Workshop on Atom Optics and Interferometry, held in Lunteren, The Netherlands, from 28 September to 2 October 2002. This was the last in a series of Workshops organized with the support of the European Community that have greatly contributed to progress in this area. The scientific part of the Workshop was managed by A Hemmerich, W Hogervorst, W Vassen and J T M Walraven, with input from members of the International Programme Committee who are listed below. The practical aspects of the organization were ably handled by Petra de Gijsel from the Vrije Universiteit in Amsterdam. The Workshop was funded by the European Science Foundation (programme BEC2000+), the European Networks 'Cold Quantum Gases (CQG)', coordinated by E Arimondo, and 'Cold Atoms and Ultraprecise Atomic Clocks (CAUAC)', coordinated by J Henningsen, by the German Physical Society (DFG), by
Universality in a 2-component fermi system at finite temperature.
Rupak, Gautam
Thermodynamic properties of a Fermi system close to the unitarity limit, where the 2-body scattering length a approaches +/-infinity, are studied in the high temperature Boltzmann regime. For dilute systems the virial expansion coefficients in the Boltzmann regime are expected, from general arguments, to be universal. A model independent finite temperature T calculation of the third virial coefficient b3(T) is presented. At the unitarity limit, b3infinity approximately 1.11 is a universal number. The energy density up to the third virial expansion is derived. These calculations are of interest in dilute neutron matter and could be tested in current atomic experiments on dilute Fermi gases near the Feshbach resonance.
EDITORIAL: The 20th European Sectional Conference on Atomic and Molecular Physics of Ionized Gases The 20th European Sectional Conference on Atomic and Molecular Physics of Ionized Gases
Petrović, Zoran Lj; Marić, Dragana; Malović, Gordana
This special issue consists of papers that are associated with invited lectures, workshop papers and hot topic papers presented at the 20th European Sectional Conference on Atomic and Molecular Physics of Ionized Gases (ESCAMPIG XX). This conference was organized in Novi Sad (Serbia) from 13 to 17 July 2010 by the Institute of Physics of the University of Belgrade. It is important to note that this is not a conference 'proceedings'. Following the initial selection process by the International Scientific Committee, all papers were submitted to the journal by the authors and have been fully peer reviewed to the standard required for publication in Plasma Sources Science and Technology (PSST). The papers are based on presentations given at the conference but are intended to be specialized technical papers covering all or part of the topic presented by the author during the meeting. The ESCAMPIG conference is a regular biennial Europhysics Conference of the European Physical Society focusing on collisional and radiative aspects of atomic and molecular physics in partially ionized gases as well as on plasma-surface interaction. The conference focuses on low-temperature plasma sciences in general and includes the following topics: Atomic and molecular processes in plasmas Transport phenomena, particle velocity distribution function Physical basis of plasma chemistry Plasma surface interaction (boundary layers, sheath, surface processes) Plasma diagnostics Plasma and discharges theory and simulation Self-organization in plasmas, dusty plasmas Upper atmospheric plasmas and space plasmas Low-pressure plasma sources High-pressure plasma sources Plasmas and gas flows Laser-produced plasmas During ESCAMPIG XX special sessions were dedicated to workshops on: Atomic and molecular collision data for plasma modeling, organized by Professors Z Lj Petrovic and N Mason Plasmas in medicine, organized by Dr N Puac and Professor G Fridman. The conference topics were represented in the
Second-order virial expansion for an atomic gas in a harmonic waveguide
Kristensen, Tom; Leyronas, Xavier; Pricoupenko, Ludovic
The virial expansion for cold two-component Fermi and Bose atomic gases is considered in the presence of a waveguide and in the vicinity of a Feshbach resonance. The interaction between atoms and the coupling with the Feshbach molecules is modeled using a quantitative separable two-channel model. The scattering phase shift in an atomic waveguide is defined. This permits us to extend the Beth-Uhlenbeck formula for the second-order virial coefficient to this inhomogeneous case.
The long-range non-additive three-body dispersion interactions for the rare gases, alkali and alkaline-earth atoms
Tang, Li-Yan; Shi, Ting-Yun; Babb, James F; Mitroy, J
The long-range non-additive three-body dispersion interaction coefficients $Z_{111}$, $Z_{112}$, $Z_{113}$, and $Z_{122}$ are computed for many atomic combinations using standard expressions. The atoms considered include hydrogen, the rare gases, the alkali atoms (up to Rb) and the alkaline-earth atoms (up to Sr). The term $Z_{111}$, arising from three mutual dipole interactions is known as the Axilrod-Teller-Muto coefficient or the DDD (dipole-dipole-dipole) coefficient. Similarly, the terms $Z_{112}$, $Z_{113}$, and $Z_{122}$ arise from the mutual combinations of dipole (1), quadrupole (2), and octupole (3) interactions between atoms and they are sometimes known, respectively, as DDQ, DDO, and DQQ coefficients. Results for the four $Z$ coefficients are given for the homonuclear trimers, for the trimers involving two like-rare-gas atoms, and for the trimers with all combinations of the H, He, Li atoms. An exhaustive compilation of all coefficients between all possible atomic combinations is presented as supp...
Simultaneous Observations of PKS 2155--304 with H.E.S.S., Fermi, RXTE and ATOM: Spectral Energy Distributions and Variability in a Low State
Energy Technology Data Exchange (ETDEWEB)
Aharonian, F.; /Heidelberg, Max Planck Inst. /Dublin Inst.; Akhperjanian, A.G.; /Yerevan Phys. Inst.; Anton, G.; /Erlangen - Nuremberg U.; Barres de Almeida, U.; /Durham U.; Bazer-Bachi, A.R.; /Toulouse, CESR; Becherini, Y.; /APC, Paris; Behera, B.; /Heidelberg Observ.; Bernlohr, K.; /Heidelberg, Max Planck Inst. /Humboldt U., Berlin; Boisson, C.; /LUTH, Meudon; Bochow, A.; /Heidelberg, Max Planck Inst.; Borrel, V.; /Toulouse, CESR; Brion, E.; /DAPNIA, Saclay; Brucker, J.; /Erlangen - Nuremberg U.; Brun, P.; /DAPNIA, Saclay; Buhler, R.; /Heidelberg, Max Planck Inst.; Bulik, T.; /Warsaw, Copernicus Astron. Ctr.; Busching, I.; /Western Ontario U.; Boutelier, T.; /Grenoble Observ.; Chadwick, P.M.; /Durham U.; Charbonnier, A.; /Paris U., VI-VII; Chaves, R.C.G.; /Heidelberg, Max Planck Inst. /Durham U. /Ecole Polytechnique /Heidelberg, Max Planck Inst. /Annecy, LAPP /Humboldt U., Berlin /Durham U. /Namibia U. /Western Ontario U. /Ecole Polytechnique /Heidelberg, Max Planck Inst. /Durham U. /APC, Paris /Heidelberg, Max Planck Inst. /Dublin Inst. /Annecy, LAPP /Grenoble Observ. /Warsaw, Copernicus Astron. Ctr. /Cracow, INP /Heidelberg, Max Planck Inst. /Heidelberg Observ. /APC, Paris /Montpellier U. /Montpellier U. /Montpellier U. /Heidelberg, Max Planck Inst. /Ecole Polytechnique /Humboldt U., Berlin /Dublin Inst. /Montpellier U. /APC, Paris /SLAC; /more authors..
We report on the first simultaneous observations that cover the optical, X-ray, and high-energy gamma-ray bands of the BL Lac object PKS 2155-304. The gamma-ray bands were observed for 11 days, between 2008 August 25 and 2008 September 6 (MJD 54704-54715), jointly with the Fermi Gamma-ray Space Telescope and the HESS atmospheric Cherenkov array, providing the first simultaneous MeV-TeV spectral energy distribution (SED) with the new generation of {gamma}-ray telescopes. The ATOM telescope and the RXTE and Swift observatories provided optical and X-ray coverage of the low-energy component over the same time period. The object was close to the lowest archival X-ray and very high energy (VHE; >100 GeV) state, whereas the optical flux was much higher. The light curves show relatively little ({approx}30%) variability overall when compared to past flaring episodes, but we find a clear optical/VHE correlation and evidence for a correlation of the X-rays with the high-energy spectral index. Contrary to previous observations in the flaring state, we do not find any correlation between the X-ray and VHE components. Although synchrotron self-Compton models are often invoked to explain the SEDs of BL Lac objects, the most common versions of these models are at odds with the correlated variability we find in the various bands for PKS 2155-304.
A new numerical approach to solve Thomas-Fermi model of an atom using bio-inspired heuristics integrated with sequential quadratic programming.
Raja, Muhammad Asif Zahoor; Zameer, Aneela; Khan, Aziz Ullah; Wazwaz, Abdul Majid
In this study, a novel bio-inspired computing approach is developed to analyze the dynamics of nonlinear singular Thomas-Fermi equation (TFE) arising in potential and charge density models of an atom by exploiting the strength of finite difference scheme (FDS) for discretization and optimization through genetic algorithms (GAs) hybrid with sequential quadratic programming. The FDS procedures are used to transform the TFE differential equations into a system of nonlinear equations. A fitness function is constructed based on the residual error of constituent equations in the mean square sense and is formulated as the minimization problem. Optimization of parameters for the system is carried out with GAs, used as a tool for viable global search integrated with SQP algorithm for rapid refinement of the results. The design scheme is applied to solve TFE for five different scenarios by taking various step sizes and different input intervals. Comparison of the proposed results with the state of the art numerical and analytical solutions reveals that the worth of our scheme in terms of accuracy and convergence. The reliability and effectiveness of the proposed scheme are validated through consistently getting optimal values of statistical performance indices calculated for a sufficiently large number of independent runs to establish its significance.
PREFACE: The 19th European Sectional Conference on Atomic and Molecular Physics of Ionized Gases Preface: The 19th European Sectional Conference on Atomic and Molecular Physics of Ionized Gases
Gordillo-Vazquez, F. J.
The 19th Europhysics Sectional Conference on the Atomic and Molecular Physics of Ionized Gases (ESCAMPIG-2008) took place in Granada (Spain) from 15 to 19 July 2008. The conference was mainly organized by the Spanish National Research Council (CSIC), with the collaboration and support of the University of Córdoba (UCO) and the Research Center for Energy, Environment and Technology (CIEMAT). It is already 35 years since the first ESCAMPIG in 1973. The first editions of ESCAMPIG were in consecutive years (1973 and 1974) but later on it became a biennial conference of the European Physical Society (EPS) initially focusing on the collisional and radiative atomic and molecular processes in low temperature plasmas. The successive ESCAMPIGs took place in Bratislava in 1976 (3rd), Essen in 1978 (4th), Dubrovnik in 1980 (5th) and so on until the last one organized in Granada in 2008 (19th), the first ESCAMPIG in Spain. A number of changes have taken place in the Granada edition of ESCAMPIG. First, the previous six topics that have remained unchanged for almost two decades (since 1990) have now been updated to become twelve new topics which, in the opinion of the International Scientific Committee (ISC), will enhance the opportunity for discussions and communication of new findings and developments in the field of low temperature plasmas. The new list of topics for ESCAMPIG is: • Atomic and molecular processes in plasmas • Transport phenomena, particle velocity distribution function • Physical basis of plasma chemistry • Plasma surface interaction (boundary layers, sheath, surface processes) • Plasma diagnostics • Plasma and dicharges theory and simulation • Self-organization in plasmas, dusty plasmas • Upper atmospheric plasmas and space plasmas • Low pressure plasma sources • High pressure plasma sources • Plasmas and gas flows • Laser produced plasmas Secondly, a new prize has been created, the `William Crookes' prize in Plasma Physics to be
Revised FINAL–REPORT NO. 2: INDEPENDENT CONFIRMATORY SURVEY SUMMARY AND RESULTS FOR THE ENRICO FERMI ATOMIC POWER PLANT, UNIT 1, NEWPORT, MICHIGAN (DOCKET NO. 50 16; RFTA 10-004) 2018-SR-02-1
Energy Technology Data Exchange (ETDEWEB)
Erika Bailey
The Enrico Fermi Atomic Power Plant, Unit 1 (Fermi 1) was a fast breeder reactor design that was cooled by sodium and operated at essentially atmospheric pressure. On May 10, 1963, the Atomic Energy Commission (AEC) granted an operating license, DPR-9, to the Power Reactor Development Company (PRDC), a consortium specifically formed to own and operate a nuclear reactor at the Fermi 1 site. The reactor was designed for a maximum capability of 430 megawatts (MW); however, the maximum reactor power with the first core loading (Core A) was 200 MW. The primary system was filled with sodium in December 1960 and criticality was achieved in August 1963. The reactor was tested at low power during the first couple years of operation. Power ascension testing above 1 MW commenced in December 1965 immediately following the receipt of a high-power operating license. In October 1966 during power ascension, zirconium plates at the bottom of the reactor vessel became loose and blocked sodium coolant flow to some fuel subassemblies. Two subassemblies started to melt and the reactor was manually shut down. No abnormal releases to the environment occurred. Forty-two months later after the cause had been determined, cleanup completed, and the fuel replaced, Fermi 1 was restarted. However, in November 1972, PRDC made the decision to decommission Fermi 1 as the core was approaching its burn-up limit. The fuel and blanket subassemblies were shipped off-site in 1973. Following that, the secondary sodium system was drained and sent off-site. The radioactive primary sodium was stored on-site in storage tanks and 55 gallon (gal) drums until it was shipped off-site in 1984. The initial decommissioning of Fermi 1 was completed in 1975. Effective January 23, 1976, DPR-9 was transferred to the Detroit Edison Company (DTE) as a 'possession only' license (DTE 2010a). This report details the confirmatory activities performed during the second Oak Ridge Institute for Science and Education
Indian Academy of Sciences (India)
IAS Admin
Fermi Transport. Joseph Samuel. Figure 1. It shows the sphere of directions in green, with three radial directions labeled. 1, 2, 3. The polarisation vectors are shown in red perpendicular to the radius vector and therefore tangential to the sphere. If the direction of a light ray changes from 1 to. 2 to 3 to 1, the polarisation vector ...
Enrico Fermi the obedient genius
Bruzzaniti, Giuseppe
This biography explores the life and career of the Italian physicist Enrico Fermi, which is also the story of thirty years that transformed physics and forever changed our understanding of matter and the universe: nuclear physics and elementary particle physics were born, nuclear fission was discovered, the Manhattan Project was developed, the atomic bombs were dropped, and the era of "big science" began. It would be impossible to capture the full essence of this revolutionary period without first understanding Fermi, without whom it would not have been possible. Enrico Fermi: The Obedient Genius attempts to shed light on all aspects of Fermi's life - his work, motivation, influences, achievements, and personal thoughts - beginning with the publication of his first paper in 1921 through his death in 1954. During this time, Fermi demonstrated that he was indeed following in the footsteps of Galileo, excelling in his work both theoretically and experimentally by deepening our understanding of the Pauli e...
The first example of commensurate adsorption of atomic gas in a MOF and effective separation of xenon from other noble gases
Wang, Hao
In industry, cryogenic rectification for separating xenon from other noble gases such as krypton and argon is an energy and capital intensive process. Here we show that a microporous metal-organic framework, namely Co 3(HCOO)6 is capable of effective capture and separation of xenon from other noble gases. Henry\\'s constant, isosteric heat of adsorption (Qst), and IAST selectivity are calculated based on single component sorption isotherms. Having the highest Qst reported to date, Co 3(HCOO)6 demonstrates high adsorption capacity for xenon and its IAST selectivity for Xe-Kr is the largest among all MOFs investigated to date. To mimic real world conditions, breakthrough experiments are conducted on Xe-Kr binary mixtures at room temperature and 1 atmosphere. The results are consistent with the calculated data. These findings show that Co 3(HCOO)6 is a promising candidate for xenon capture and purification. Our gas adsorption measurements and molecular simulation study also reveal that the adsorption of xenon represents the first example of commensurate adsorption of atomic gases near ambient conditions. © 2014 The Royal Society of Chemistry.
Pairing fluctuations in trapped Fermi gases
DEFF Research Database (Denmark)
Bruun, Georg Morten; Minguzzi, Anna; Rosario, F.
A0530F- Fermion-systems-and-electron-gas-quantum-statistical-mechanics; A0540-Fluctuation-phenomena-random-processes-and-Brownian-motion......A0530F- Fermion-systems-and-electron-gas-quantum-statistical-mechanics; A0540-Fluctuation-phenomena-random-processes-and-Brownian-motion...
Strongly Interacting Fermi Gases In Two Dimensions
electron spin, rather than of charge, is being explored as a new way to carry information. Neutrino transport energizes supernova explosions following...Eb of fermion pairs increases in surprising agreement with mean -field theory for the BEC-BCS crossover in two dimensions...Neutrino transport energizes supernova explosions following the collapse of a dying star, and hydrodynamic transport of the quark-gluon plasma
Strongly Interacting Fermi Gases in Two Dimensions
provide a benchmark for many-body theories on strongly Figure 1 Figure 1 Evolution of Fermion Pairing from Three to Two Dimensions. Radio -Frequency...form: H = ~ 2k2 2m − gµB ~ S · (B(D) + B(R) + B(Z)), (1) where g is the electron g-factor, µB is the Bohr magneton and S is the electron spin. The...in spin distributions between AXMSPs and radio MSPs, because radio MSPs, which have weak surface magnetic field strengths, could not spin down by the
On the size and structure of helium snowballs formed around charged atoms and clusters of noble gases.
Bartl, Peter; Leidlmair, Christian; Denifl, Stephan; Scheier, Paul; Echt, Olof
Helium nanodroplets doped with argon, krypton, or xenon are ionized by electrons and analyzed in a mass spectrometer. HenNgx(+) ions containing up to seven noble gas (Ng) atoms and dozens of helium atoms are identified; the high resolution of the mass spectrometer combined with advanced data analysis make it possible to unscramble contributions from isotopologues that have the same nominal mass but different numbers of helium or Ng atoms, such as the magic He20(84)Kr2(+) and the isobaric, nonmagic He41(84)Kr(+). Anomalies in these ion abundances reveal particularly stable ions; several intriguing patterns emerge. Perhaps most astounding are the results for HenAr(+), which show evidence for three distinct, solid-like solvation shells containing 12, 20, and 12 helium atoms. This observation runs counter to the common notion that only the first solvation shell is solid-like but agrees with calculations by Galli et al. for HenNa(+) [J. Phys. Chem. A 2011, 115, 7300] that reveal three shells of icosahedral symmetry. HenArx(+) (2 ≤ x ≤ 7) ions appear to be especially stable if they contain a total of n + x = 19 atoms. A sequence of anomalies in the abundance distribution of HenKrx(+) suggests that rings of six helium atoms are inserted into the solvation shell each time a krypton atom is added to the ionic core, from Kr(+) to Kr3(+). Previously reported strong anomalies at He12Kr2(+) and He12Kr3(+) [Kim , J. H.; et al. J. Chem. Phys. 2006, 124, 214301] are attributed to a contamination. Only minor local anomalies appear in the distributions of HenXex(+) (x ≤ 3). The distributions of HenKr(+) and HenXe(+) show strikingly similar, broad features that are absent from the distribution of HenAr(+); differences are tentatively ascribed to the very different fragmentation dynamics of these ions.
Effects of classical stochastic webs on the quantum dynamics of cold atomic gases in a moving optical lattice
Welch, N.; Greenaway, M. T.; Fromhold, T. M.
We introduce and investigate a system that uses temporal resonance-induced phase-space pathways to create strong coupling between an atomic Bose-Einstein condensate and a traveling optical lattice potential. We show that these pathways thread both the classical and quantum phase space of the atom cloud, even when the optical lattice potential is arbitrarily weak. The topology of the pathways, which form weblike patterns, can by controlled by changing the amplitude and period of the optical lattice. In turn, this control can be used to increase and limit the BEC's center-of-mass kinetic energy to prespecified values. Surprisingly, the strength of the atom-lattice interaction and resulting BEC heating of the center-of-mass motion is enhanced by the repulsive interatomic interactions.
Will Allis Prize for the Study of Ionized Gases Lecture: Electron and Photon Collisions with Atoms and Molecules
Burke, Philip G.
After a brief historical introduction this talk will review the broad range of collision processes involving electron and photon collisions with atoms and molecules that are now being considered. Their application in the analysis of astronomical spectra, atmospheric observations and laboratory plasmas will be considered. The talk will review the R-matrix computational method which has been widely used by international collaborations and by other scientists in the field to obtain accurate scattering amplitudes and cross sections of importance in these applications. Results of some recent calculations of electron and photon collisions with atoms and molecules will be presented. In conclusion some challenges for future research will be briefly discussed.
Enhancing Kondo coupling in alkaline-earth-metal atomic gases with confinement-induced resonances in mixed dimensions
Cheng, Yanting; Zhang, Ren; Zhang, Peng; Zhai, Hui
The Kondo effect describes the spin-exchange interaction between localized impurities and itinerant fermions. The ultracold alkaline-earth atomic gas provides a natural platform for quantum simulation of the Kondo model, utilizing its long-lived clock state and the nuclear-spin exchange interaction between clock state and ground state. One of the key issue now is whether the Kondo temperature can be high enough to be reached in current experiments, for which we have proposed to use transverse confinement to confine atoms into a one-dimensional tube and to use the confinement-induced resonance to enhance Kondo coupling. In this work, we further consider the (1 +0 ) -dimensional scattering problem when the clock state is further confined by an axial harmonic confinement. We show that this axial confinement for the clock-state atoms not only plays a role for localizing them, but can also act as an additional control knob to reach the confinement-induced resonance. We show that, in the presence of both the transverse and the axial confinements, the confinement-induced resonance can be reached in the practical conditions and the Kondo effect can be attainable in this system.
Precision measurements of cross sections of inelastic processes realized in collisions of alkali metal ions with atoms of rare gases
Lomsadze, R A; Mosulishvili, N O; Kezerashvili, R Ya
This work presents a multifaceted experimental study of collisions of Na$^{+}$ and K$^{+}$ ions in the energy range 0.5 -- 10 keV with He and Ar atoms. Absolute cross sections for charge-exchange, ionization, stripping and excitation were measured using a refined version of the transfer electric field method, angle- and energy-dependent collection of product ions, energy loss, and optical spectroscopy. The experimental data and the schematic correlation diagrams have been employed to analyze and determine the mechanisms for these processes.
Signals of Bose Einstein condensation and Fermi quenching in the decay of hot nuclear systems
Directory of Open Access Journals (Sweden)
P. Marini
Full Text Available We report on first experimental observations of nuclear fermionic and bosonic components displaying different behaviours in the decay of hot Ca projectile-like sources produced in mid-peripheral collisions at sub-Fermi energies. The experimental setup, constituted by the coupling of the INDRA 4π detector array to the forward angle VAMOS magnetic spectrometer, allowed to reconstruct the mass, charge and excitation energy of the decaying hot projectile-like sources. By means of quantum-fluctuation analysis techniques, temperatures and local partial densities of bosons and fermions could be correlated to the excitation energy of the reconstructed system. The results are consistent with the production of dilute mixed systems of bosons and fermions, where bosons experience higher phase-space and energy density as compared to the surrounding fermionic gas. Our findings recall phenomena observed in the study of Bose condensates and Fermi gases in atomic traps despite the different scales.
Signals of Bose Einstein condensation and Fermi quenching in the decay of hot nuclear systems
Energy Technology Data Exchange (ETDEWEB)
Marini, P., E-mail: firstname.lastname@example.com [Grand Accélérateur National d' Ions Lourds, Bd. Henri Becquerel, BP 55027, 14076 Caen (France); Zheng, H. [Cyclotron Institute, Texas A& M University, College Station, TX-77843 (United States); Laboratori Nazionali del Sud, INFN, via Santa Sofia, 62, 95123 Catania (Italy); Boisjoli, M. [Grand Accélérateur National d' Ions Lourds, Bd. Henri Becquerel, BP 55027, 14076 Caen (France); Laboratoire de Physique Nucléaire, Université Laval, Québec, G1V 0A6 (Canada); Verde, G. [Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay, 91406 Orsay Cedex (France); INFN – Sezione di Catania, via Santa Sofia, 64, 95123 Catania (Italy); Chbihi, A. [Grand Accélérateur National d' Ions Lourds, Bd. Henri Becquerel, BP 55027, 14076 Caen (France); Napolitani, P.; Ademard, G. [Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay, 91406 Orsay Cedex (France); Augey, L. [Laboratoire de Physique Corpusculaire, ENSICAEN, Université de Caen Basse Normandie, CNRS/IN2P3, F-14050 Caen Cedex (France); Bhattacharya, C. [Variable Energy Cyclotron Center, Kolkata (India); Borderie, B. [Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay, 91406 Orsay Cedex (France); Bougault, R. [Laboratoire de Physique Corpusculaire, ENSICAEN, Université de Caen Basse Normandie, CNRS/IN2P3, F-14050 Caen Cedex (France); and others
We report on first experimental observations of nuclear fermionic and bosonic components displaying different behaviours in the decay of hot Ca projectile-like sources produced in mid-peripheral collisions at sub-Fermi energies. The experimental setup, constituted by the coupling of the INDRA 4π detector array to the forward angle VAMOS magnetic spectrometer, allowed to reconstruct the mass, charge and excitation energy of the decaying hot projectile-like sources. By means of quantum-fluctuation analysis techniques, temperatures and local partial densities of bosons and fermions could be correlated to the excitation energy of the reconstructed system. The results are consistent with the production of dilute mixed systems of bosons and fermions, where bosons experience higher phase-space and energy density as compared to the surrounding fermionic gas. Our findings recall phenomena observed in the study of Bose condensates and Fermi gases in atomic traps despite the different scales.
... atmosphere, creating a greenhouse effect that results in global warming and climate change. Many gases exhibit these greenhouse properties. Some gases occur naturally and are also produced by human activities. Some, such as industrial gases, are exclusively ...
Topological insulators in cold-atom gases with non-Abelian gauge fields: the role of interactions
Energy Technology Data Exchange (ETDEWEB)
Orth, Peter Philipp [Institut fuer Theorie der Kondensierten Materie, Karlsruher Institut fuer Technologie, 76128 Karlsruhe (Germany); Cocks, Daniel; Buchhold, Michael; Hofstetter, Walter [Institut fuer Theoretische Physik, Goethe Universitaet, 60438 Frankfurt am Main (Germany); Rachel, Stephan [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Le Hur, Karyn [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Center for Theoretical Physics, Ecole Polytechnique, 91128 Palaiseau Cedex (France)
With the recent technological advance of creating (non)-Abelian gauge fields for ultracold atoms in optical lattices, it becomes possible to study the interplay of topological phases and interactions in these systems. Specifically, we consider a spinful and time-reversal invariant version of the Hofstadter problem. In addition, we allow for a hopping term which does not preserve S{sub z} spin symmetry and a staggered sublattice potential. Without interactions, the parameters can be tuned such that the system is a topological insulator. Using a combination of analytical techniques and the powerful real-space dynamical mean-field (R-DMFT) method, we discuss the effect of interactions and determine the interacting phase diagram.
Optimized sympathetic cooling of atomic mixtures via fast adiabatic strategies
Energy Technology Data Exchange (ETDEWEB)
Choi, Stephen; Sundaram, Bala [Department of Physics, University of Massachusetts, Boston, Massachusetts 02125 (United States); Onofrio, Roberto [Dipartimento di Fisica ' ' Galileo Galilei' ' , Universita di Padova, Via Marzolo 8, Padova I-35131 (Italy); Department of Physics, University of Massachusetts, Boston, Massachusetts 02125 (United States); Institute for Theoretical Atomic, Molecular and Optical Physics (ITAMP), Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)
We discuss fast frictionless cooling techniques in the framework of sympathetic cooling of cold atomic mixtures. It is argued that optimal cooling of an atomic species--in which the deepest quantum degeneracy regime is achieved--may be obtained by means of sympathetic cooling with another species whose trapping frequency is dynamically changed to maintain constancy of the Lewis-Riesenfeld adiabatic invariant. Advantages and limitations of this cooling strategy are discussed, with particular regard to the possibility of cooling Fermi gases to a deeper degenerate regime.
Analytical pair correlations in ideal quantum gases: temperature-dependent bunching and antibunching.
Bosse, J; Pathak, K N; Singh, G S
The fluctuation-dissipation theorem together with the exact density response spectrum for ideal quantum gases has been utilized to yield a new expression for the static structure factor, which we use to derive exact analytical expressions for the temperature-dependent pair distribution function g(r) of the ideal gases. The plots of bosonic and fermionic g(r) display "Bose pile" and "Fermi hole" typically akin to bunching and antibunching as observed experimentally for ultracold atomic gases. The behavior of spin-scaled pair correlation for fermions is almost featureless, but bosons show a rich structure including long-range correlations near T(c). The coherent state at T=0 shows no correlation at all, just like single-mode lasers. The depicted decreasing trend in correlation with decrease in temperature for T
Thermodynamics of Quantum Gases for the Entire Range of Temperature
Biswas, Shyamal; Jana, Debnarayan
We have analytically explored the thermodynamics of free Bose and Fermi gases for the entire range of temperature, and have extended the same for harmonically trapped cases. We have obtained approximate chemical potentials for the quantum gases in closed forms of temperature so that the thermodynamic properties of the quantum gases become…
Closed-Form Solutions of the Thomas-Fermi in Heavy Atoms and the Langmuir-Blodgett in Current Flow ODEs in Mathematical Physics
Directory of Open Access Journals (Sweden)
Efstathios E. Theotokoglou
Full Text Available Two kinds of second-order nonlinear, ordinary differential equations (ODEs appearing in mathematical physics are analyzed in this paper. The first one concerns the Thomas-Fermi (TF equation, while the second concerns the Langmuir-Blodgett (LB equation in current flow. According to a mathematical methodology recently developed, the exact analytic solutions of both TF and LB ODEs are proposed. Both of these are nonlinear of the second order and by a series of admissible functional transformations are reduced to Abel's equations of the second kind of the normal form. The closed form solutions of the TF and LB equations in the phase and physical plane are given. Finally a new interesting result has been obtained related to the derivative of the TF function at the limit.
Two-stage crossed beam cooling with ⁶Li and ¹³³Cs atoms in microgravity.
Luan, Tian; Yao, Hepeng; Wang, Lu; Li, Chen; Yang, Shifeng; Chen, Xuzong; Ma, Zhaoyuan
Applying the direct simulation Monte Carlo (DSMC) method developed for ultracold Bose-Fermi mixture gases research, we study the sympathetic cooling process of 6Li and 133Cs atoms in a crossed optical dipole trap. The obstacles to producing 6Li Fermi degenerate gas via direct sympathetic cooling with 133Cs are also analyzed, by which we find that the side-effect of the gravity is one of the main obstacles. Based on the dynamic nature of 6Li and 133Cs atoms, we suggest a two-stage cooling process with two pairs of crossed beams in microgravity environment. According to our simulations, the temperature of 6Li atoms can be cooled to T = 29.5 pK and T/TF = 0.59 with several thousand atoms, which propose a novel way to get ultracold fermion atoms with quantum degeneracy near pico-Kelvin.
Long-Lived Spin-Orbit-Coupled Degenerate Dipolar Fermi Gas
Directory of Open Access Journals (Sweden)
Nathaniel Q. Burdick
Full Text Available We describe the creation of a long-lived spin-orbit-coupled gas of quantum degenerate atoms using the most magnetic fermionic element, dysprosium. Spin-orbit coupling arises from a synthetic gauge field created by the adiabatic following of degenerate dressed states composed of optically coupled components of an atomic spin. Because of dysprosium's large electronic orbital angular momentum and large magnetic moment, the lifetime of the gas is limited not by spontaneous emission from the light-matter coupling, as for gases of alkali-metal atoms, but by dipolar relaxation of the spin. This relaxation is suppressed at large magnetic fields due to Fermi statistics. We observe lifetimes up to 400 ms, which exceeds that of spin-orbit-coupled fermionic alkali atoms by a factor of 10–100 and is close to the value obtained from a theoretical model. Elastic dipolar interactions are also observed to influence the Rabi evolution of the spin, revealing an interacting fermionic system. The long lifetime of this weakly interacting spin-orbit-coupled degenerate Fermi gas will facilitate the study of quantum many-body phenomena manifest at longer time scales, with exciting implications for the exploration of exotic topological quantum liquids.
Universal spin transport in a strongly interacting Fermi gas.
Sommer, Ariel; Ku, Mark; Roati, Giacomo; Zwierlein, Martin W
Transport of fermions, particles with half-integer spin, is central to many fields of physics. Electron transport runs modern technology, defining states of matter such as superconductors and insulators, and electron spin is being explored as a new carrier of information. Neutrino transport energizes supernova explosions following the collapse of a dying star, and hydrodynamic transport of the quark-gluon plasma governed the expansion of the early Universe. However, our understanding of non-equilibrium dynamics in such strongly interacting fermionic matter is still limited. Ultracold gases of fermionic atoms realize a pristine model for such systems and can be studied in real time with the precision of atomic physics. Even above the superfluid transition, such gases flow as an almost perfect fluid with very low viscosity when interactions are tuned to a scattering resonance. In this hydrodynamic regime, collective density excitations are weakly damped. Here we experimentally investigate spin excitations in a Fermi gas of (6)Li atoms, finding that, in contrast, they are maximally damped. A spin current is induced by spatially separating two spin components and observing their evolution in an external trapping potential. We demonstrate that interactions can be strong enough to reverse spin currents, with components of opposite spin reflecting off each other. Near equilibrium, we obtain the spin drag coefficient, the spin diffusivity and the spin susceptibility as a function of temperature on resonance and show that they obey universal laws at high temperatures. In the degenerate regime, the spin diffusivity approaches a value set by [planck]/m, the quantum limit of diffusion, where [planck]/m is Planck's constant divided by 2π and m the atomic mass. For repulsive interactions, our measurements seem to exclude a metastable ferromagnetic state.
Universal Quantum Viscosity in a Unitary Fermi Gas
Cao, Chenglin
Unitary Fermi gases, first observed in 2002, have been widely studied as they provide model systems for tabletop research on a variety of strongly coupled systems, including the high temperature superconductors, quark-gluon plasmas and neutron stars. A two component 6Li unitary Fermi gas is created through a collisional Feshbach resonance centered around 834G, using all-optical trapping and cooling methods. In the vicinity of the Feshbach resonance, the atoms are strongly interacting and exhibit universal behaviors, where the equilibrium thermodynamic properties and transport coefficients are universal functions of the density n and temperature T. Thus, unitary Fermi gases provide a paradigm to study nonperturbative many-body physics, which is of fundamental significance and field-crossing interests. This dissertation reports the measurement of the quantum shear viscosity in a 6Li unitary Fermi gas, which is the first measurement of transport coefficients for unitary Fermi gases. Two hydrodynamic experiments are employed to measure the shear viscosity eta in different temperature regimes: the anisotropic expansion for the high temperature regime and the radial breathing mode for the low temperature regime. In order to consistently and quantitatively extract the shear viscosity from these two experiments, the hydrodynamic theory is utilized to derive the universal hydrodynamic equations, which include both friction force and heating arising from frictions. These equations are simplified and solved, considering the universal properties of unitary Fermi gases as well as the specific conditions for each experiment. Using these universal hydrodynamic equations, shear viscosity is extracted from the anisotropic expansion conducted at high temperatures and the predicted eta ∝ T3/2 scaling is demonstrated. The demonstration of the high temperature scaling sets a benchmark for measuring viscosity at low temperatures. For the low temperature breathing mode experiment, the
Born, Max
The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.
Fermi: a physicist in the upheaval; Fermi: un physicien dans la tourmente
Energy Technology Data Exchange (ETDEWEB)
Maria, M. de
This book summarizes the life, works and complex personality of the Italian physicist Enrico Fermi (1901-1954) whose myth is linked with the political upheaval of the 2. world war: the youth of an autodidact, the theorician and the quantum mechanics, his invention of a quantum statistics, the weak interaction theory, his works on artificial radioactivity, the end of the Fermi team and his exile in the USA, the secrete researches at the university of Columbia and the birth of the first atomic 'pile' (December 2, 1942), the building of Los Alamos center and the Alamogordo explosion test, the disagreements among the physicists of the Manhattan project and the position of Fermi, Fermi's contribution in the H-bomb construction, the creation of the physics school of Chicago, the Oppenheimer spying affair. (J.S.)
Energy Technology Data Exchange (ETDEWEB)
Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)
The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.
1. This view from NASA's Fermi Gamma-ray Space Telescope is the deepest and best-resolved portrait of the gamma-ray sky to date. The image shows how the sky appears at energies more than 150 million times greater than that of visible light. Among the signatures of bright pulsars and active galaxies is something familiar -- a faint path traced by the sun. (Credit: NASA/DOE/Fermi LAT Collaboration) 2. The Large Area Telescope (LAT) on Fermi detects gamma-rays through matter (electrons) and antimatter (positrons) they produce after striking layers of tungsten. (Credit: NASA/Goddard Space Flight Center Conceptual Image Lab)
An interpolatory ansatz captures the physics of one-dimensional confined Fermi systems
DEFF Research Database (Denmark)
Andersen, Molte Emil Strange; Salami Dehkharghani, Amin; Volosniev, A. G.
Interacting one-dimensional quantum systems play a pivotal role in physics. Exact solutions can be obtained for the homogeneous case using the Bethe ansatz and bosonisation techniques. However, these approaches are not applicable when external confinement is present. Recent theoretical advances...... beyond the Bethe ansatz and bosonisation allow us to predict the behaviour of one-dimensional confined systems with strong short-range interactions, and new experiments with cold atomic Fermi gases have already confirmed these theories. Here we demonstrate that a simple linear combination of the strongly...... interacting solution with the well-known solution in the limit of vanishing interactions provides a simple and accurate description of the system for all values of the interaction strength. This indicates that one can indeed capture the physics of confined one-dimensional systems by knowledge of the limits...
Superfluidity in an Atomic Gas of Strongly Interacting Fermions
Ketterle, Wolfgang
What is the benefit of realizing superfluidity in a gas a million times more dilute than air? Such systems consist of well-separated atoms which can be observed and manipulated with the control and precision of atomic physics, and which can be treated with first-principles calculations. By implementing scattering resonances, we have realized the strong-coupling limit of the Bardeen Schrieffer-Cooper (BCS) mechanism and observed a normalized transition temperature of 15% of the Fermi temperature, higher than in any superconductor. By tuning the strength of the interactions, the BEC-BCS crossover is realized. When the population of the two spin states is imbalanced, pairing is frustrated; and superfluidity is quenched at the Chandrasekhar-Clogston limit. These studies illustrate a new approach to condensed-matter physics where many-body Hamiltonians are realized in dilute atomic gases.
National Aeronautics and Space Administration — Fermi is a powerful space observatory that will open a wide window on the universe. Gamma rays are the highest-energy form of light, and the gamma-ray sky is...
National Aeronautics and Space Administration — All analysis results presented here are preliminary and are not intended as an official catalog of Fermi-LAT detected GRBs. Please consult the table's caveat page...
Enrico Fermi centenary exhibition seminar
Maximilien Brice
Photo 01: Dr. Juan Antonio Rubio, Leader of the Education and Technology Transfer Division and CERN Director General, Prof. Luciano Maiani. Photo 03: Luciano Maiani, Welcome and Introduction Photo 09: Antonino Zichichi, The New 'Centro Enrico Fermi' at Via Panisperna Photos 10, 13: Ugo Amaldi, Fermi at Via Panisperna and the birth of Nuclear Medicine Photo 14: Jack Steinberger, Fermi in Chicago Photo 18: Valentin Telegdi, A close-up of Fermi Photo 21: Arnaldo Stefanini, Celebrating Fermi's Centenary in Documents and Pictures.
Meulenbelt, J
Acute inhalation injury can result from the use of household cleaning agents (e.g. chlorine, ammonia), industrial or combustion gases (e.g. sulfur dioxide, nitrogen oxides) or bioterrorism. The severity of the injury is to a great extent determined by the circumstances of exposure. If exposure was
A long-lived spin-orbit-coupled degenerate dipolar Fermi gas
Burdick, Nathaniel Q; Lev, Benjamin L
We describe the creation of a long-lived spin-orbit-coupled gas of quantum degenerate atoms using the most magnetic fermionic element, dysprosium. Spin-orbit-coupling arises from a synthetic gauge field created by the adiabatic following of degenerate dressed states comprised of optically coupled components of an atomic spin. Because of dysprosium's large electronic orbital angular momentum and large magnetic moment, the lifetime of the gas is limited not by spontaneous emission from the light-matter coupling, as for gases of alkali-metal atoms, but by dipolar relaxation of the spin. This relaxation is suppressed at large magnetic fields due to Fermi statistics. We observe lifetimes up to 400 ms, which exceeds that of spin-orbit-coupled fermionic alkali atoms by a factor of 10-100, and is close to the value obtained from a theoretical model. Elastic dipolar interactions are also observed to influence the Rabi evolution of the spin, revealing an interacting fermionic system. The long lifetime of this weakly in...
Enrico Fermi exhibition at CERN
A touring exhibition celebrating the centenary of Enrico Fermi's birth in 1901 will be on display at CERN (Main Building, Mezzanine) from 12-27 September. You are cordially invited to the opening celebration on Thursday 12 September at 16:00 (Main Building, Council Chamber), which will include speechs from: Luciano Maiani Welcome and Introduction Arnaldo Stefanini Celebrating Fermi's Centenary in Documents and Pictures Antonino Zichichi The New 'Centro Enrico Fermi' at Via Panisperna Ugo Amaldi Fermi at Via Panisperna and the birth of Nuclear Medicine Jack Steinberger Fermi in Chicago Valentin Telegdi A Close-up of Fermi and the screening of a documentary video about Fermi: Scienziati a Pisa: Enrico Fermi (Scientists at Pisa: Enrico Fermi) created by Francesco Andreotti for La Limonaia from early film, photographs and sound recordings (In Italian, with English subtitles - c. 30 mins). This will be followed by an aperitif on the Mezz...
Cold and trapped metastable noble gases
Vassen, W.; Cohen-Tannoudji, C.; Leduc, M.; Boiron, D.; Westbrook, C.I.; Truscott, A.; Baldwin, K.; Birkl, G.; Cancio, P.; Trippenbach, M.
Experimental work on cold, trapped metastable noble gases is reviewed. The aspects which distinguish work with these atoms from the large body of work on cold, trapped atoms in general is emphasized. These aspects include detection techniques and collision processes unique to metastable atoms.
Formation of noble-gas hydrides and decay of solvated protons revisited: diffusion-controlled reactions and hydrogen atom losses in solid noble gases.
Tanskanen, Hanna; Khriachtchev, Leonid; Lignell, Antti; Räsänen, Markku; Johansson, Susanna; Khyzhniy, Ivan; Savchenko, Elena
UV photolysis and annealing of C2H2/Xe, C2H2/Xe/Kr, and HBr/Xe matrices lead to complicated photochemical processes and reactions. The dominating products in these experiments are noble-gas hydrides with general formula HNgY (Ng = noble-gas atom, Y = electronegative fragment). We concentrate on distinguishing the local and global mobility and losses of H atoms, barriers of the reactions, and the decay of solvated protons. Different deposition temperatures change the amount of lattice imperfections and thus the amount of traps for H atoms. The averaged distance between reacting species influencing the reaction kinetics is controlled by varying the precursor concentration. A number of solid-state processes connected to the formation of noble-gas hydrides and decay of solvated protons are discussed using a simple kinetic model. The most efficient formation of noble-gas hydrides is connected with global (long-range) mobility of H atoms leading to the H + Xe + Y reaction. The highest concentration of noble-gas hydrides was obtained in matrices of highest optical quality, which probably have the lowest concentration of defects and H-atom losses. In matrices with high amount of geometrical imperfections, the product formation is inefficient and dominated by a local (short-range) process. The decay of solvated protons is rather local than a global process, which is different from the formation of noble-gas molecules. However, the present data do not allow distinguishing local proton and electron mobilities. Our previous results indicate that these are electrons which move to positively-charged centers and neutralize them. It is believed that the image obtained here for solid xenon is applicable to solid krypton whereas the case of argon deserves special attention.
In only 10 months of scientific activity, the Fermi space observatory has already collected an unprecedented wealth of information on some of the most amazing objects in the sky. In a recent talk at CERN, Luca Latronico, a member of the Fermi collaboration, explained some of their findings and emphasized the strong links between High Energy Physics (HEP) and High Energy Astrophysics (HEA). The Fermi gamma-ray telescope was launched by NASA in June 2008. After about two months of commissioning it started sending significant data back to the Earth. Since then, it has made observations that are changing our view of the sky: from discovering a whole new set of pulsars, the greatest total energy gamma-ray burst ever, to detecting an unexplained abundance of high-energy electrons that could be a signature of dark matter, to producing a uniquely rich and high definition sky map in gamma-rays. The high performance of the instrument comes as ...
From few to many. Ultracold atoms in reduced dimensions
Energy Technology Data Exchange (ETDEWEB)
Wenz, Andre Niklas
This thesis reports on experimental studies exploring few and many-body physics of ultracold Bose and Fermi gases with reduced dimensionality. These experiments illustrate the versatility and great amount of control over the particle number, the interaction and other degrees of freedom, like the spin, that these generic quantum systems offer. In the first part of this thesis, we use quasi one-dimensional few-particle systems of one to ten fermionic atoms to investigate the crossover from few to many-body physics. This is achieved by measuring the interaction energy between a single impurity atom in a state vertical stroke ↓ right angle which repulsively interacts with an increasing number of majority atoms in a state vertical stroke ↑ right angle. We find that the system quickly approaches the results from the many-body theory, which describes the behavior of a single impurity immersed in a Fermi sea of an infinite number of majority particles. The second part of this thesis presents studies of the time evolution of a bosonic F=1 spinor BEC of {sup 87}Rb atoms. In this system, we investigate the emergence and coarsening of ferromagnetic spin textures from initially unmagnetized samples. While the ferromagnetic domains grow, we observe the development of a spin space anisotropy which is in agreement with the predicted phase-diagram. The last part of this thesis presents our first steps towards the investigation of phase coherence of quasi two-dimensional quantum gases in the crossover from bosonic molecules to fermionic atoms.
Model for overscreened Kondo effect in ultracold Fermi gas
Kuzmenko, I.; Kuzmenko, T.; Avishai, Y.; Kikoin, K.
The feasibility of realizing the overscreened Kondo effect in ultracold Fermi gas of atoms with spin s ≥ 3/2 in the presence of a localized magnetic impurity atom is proved realistic. Specifying (as a mere example) a system of ultracold 22Na Fermi gas and a trapped 6Li impurity, the mechanism of exchange interaction between the Na and Li atoms is elucidated and the exchange constant is found to be positive (antiferromagnetic). The corresponding exchange Hamiltonian is derived, and the Kondo temperature is estimated at the order of 500 nK. Within a weak-coupling renormalization group scheme, it is shown that the coupling renormalizes to the non-Fermi-liquid fixed point. An observable displaying multichannel features even in the weak-coupling regime is the impurity magnetization that is negative for T ≫TK and becomes positive with decreasing temperature.
On the Dynamics of the Fermi-Bose model
DEFF Research Database (Denmark)
Ögren, Magnus
In this talk we formulate and prove results for the exponential matrix representing the dynamics of the Fermi-Bose model in an undepleted bosonic field approximation. A recent application of this model is molecular dimmers dissociating into its atomic compounds. The problem is solved in D spatial...... molecular Bose-Einstein condensate.......In this talk we formulate and prove results for the exponential matrix representing the dynamics of the Fermi-Bose model in an undepleted bosonic field approximation. A recent application of this model is molecular dimmers dissociating into its atomic compounds. The problem is solved in D spatial...
Study of total ionization by {alpha} particles, in pure gases and gaseous mixtures containing metastable atoms, as a function of temperature; Etude de l'ionisation totale par les paricules {alpha}, dans les gaz purs et les melanges gazeux contenant des atomes metastables, en fonction de la temperature
Energy Technology Data Exchange (ETDEWEB)
Bristeau, P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
Experiments have been carried out on the total ionization by alpha particles, in pure gases and gaseous mixtures containing metastable atoms, as a function of temperature. Using a different experimental method, the results for the mean ionization energy at 300 K given by Jesse in 1953 have been confirmed to within 1 per cent. It is established that in pure gases the mean energy W required to form a pair of ions remains constant as the temperature varies from 77 to 300 K. It is shown that there is a temperature effect for W in binary gas mixtures of the type A-B containing meta-stable atoms A{sup *} and an 'impurity' B. A systematic study is made of the change {delta}W in W as a function of the temperature and of the B 'impurity' concentration in the mixtures Ne - Ar, Ne - Kr, Ne - H{sub 2}, Ne - N{sub 2}, Ne - CH{sub 4} and He - Ar. Experiments have been carried out on a ternary gas mixture of the type A - B - C, where C is a second ionizable 'impurity' added to the binary mixture A - B; they show the existence of excited atoms B{sup *} formed from the 'impurity' B. Finally, it is shown that the amount of metastable atoms formed in a pure gas must be very close to the number N{sub 0} of ion pairs, and that there must exist a correlation between the number N{sub 0} of ion pairs and the number {approx_equal} N{sub 0} of metastable atoms created in the pure rare gases. (author) [French] On realise des experiences sur l'ionisation totale par les particules alpha, dans les gaz purs et les melanges gazeux contenant des atomes metastables, en fonction de la temperature. Avec une methode experimentale differente, on retrouve a mieux que 1 pour cent pres les valeurs de l'energie moyenne d'ionisation que JESSE a obtenues en 1953 et a 300 K. On etablit que dans les gaz purs, l'energie moyenne W pour creer une paire d'ions demeure constante, quand la temperature varie entre 77 et 300 K. On met en evidence un
Many-body pairing in a two-dimensional Fermi gas
Energy Technology Data Exchange (ETDEWEB)
Neidig, Mathias
This thesis reports on experiments conducted in a single layer, quasi two-dimensional, two-component ultracold Fermi gas in the strongly interacting regime. Ultracold gases can be used to simulate key aspects of more complicated systems like for example cuprates which show high-T{sub c} superconductivity. The momentum distribution of a sample of bosonic dimers in a quasi-2D square lattice geometry was measured to obtain the coherence properties. For shallow lattices, sharp peaks in the momentum distribution, indicating coherence, were observed at zero momentum as well as at positive and negative lattice momenta along each axis. For deeper lattices, heating impeded the ability to prepare a Mott-insulator. A spatially resolved radio-frequency spectroscopy was employed for a quasi-2D Fermi gas in the normal phase throughout the BEC-BCS crossover. The interaction induced energy shifts were measured in the strongly interacting region where they can be on the order of the Fermi energy and thus the local resolution is crucial. Furthermore, the onset of pairing in the strongly interacting region was measured as a function of temperature and it was shown that the fraction of free atoms decreases faster than expected from thermal non-interacting theory. At last, the pairing gap was measured using an imbalanced sample. On the BEC side it was found to be in very good agreement with two-body physics as expected. In the strongly interacting regime, however, a deviation from two-body physics indicates that here many-body effects play a role and thus further studies are required.
Fluctuations and phase transitions in Larkin-Ovchinnikov liquid-crystal states of a population-imbalanced resonant Fermi gas
Radzihovsky, Leo
Motivated by a realization of imbalanced Feshbach-resonant atomic Fermi gases, we formulate a low-energy theory of the Fulde-Ferrell and the Larkin-Ovchinnikov (LO) states and use it to analyze fluctuations, stability, and phase transitions in these enigmatic finite momentum-paired superfluids. Focusing on the unidirectional LO pair-density-wave state, which spontaneously breaks the continuous rotational and translational symmetries, we show that it is characterized by two Goldstone modes, corresponding to a superfluid phase and a smectic phonon. Because of the liquid-crystalline "softness" of the latter, at finite temperature the three-dimensional state is characterized by a vanishing LO order parameter, quasi-Bragg peaks in the structure and momentum distribution functions, and a "charge"-4, paired-Cooper-pairs, off-diagonal long-range order, with a superfluid-stiffness anisotropy that diverges near a transition into a nonsuperfluid state. In addition to conventional integer vortices and dislocations, the LO superfluid smectic exhibits composite half-integer vortex-dislocation defects. A proliferation of defects leads to a rich variety of descendant states, such as the charge-4 superfluid and Fermi-liquid nematics and topologically ordered nonsuperfluid states, that generically intervene between the LO state and the conventional superfluid and the polarized Fermi liquid at low and high imbalance, respectively. The fermionic sector of the LO gapless superconductor is also quite unique, exhibiting a Fermi surface of Bogoliubov quasiparticles associated with the Andreev band of states, localized on the array of the LO domain walls.
Effect of the medium on intramolecular H-atom tunneling: cis-trans conversion of formic acid in solid matrixes of noble gases.
Trakhtenberg, Leonid I; Fokeyev, Anatoly A; Zyubin, Alexander S; Mebel, Alexander M; Lin, S H
Intramolecular tunneling of a hydrogen atom in formic acid at low temperatures has been studied theoretically on the basis of quantum-chemical modeling of HCOOH@Nb(12) clusters. Three noble matrixes (Ar, Kr, and Xe) are considered. Energetic and geometric parameters as well as vibrational frequencies for the formic acid in cis and trans configurations surrounded by 12 Nb atoms are calculated within the frame of the MP2 approach with extended basis sets. The rate constant of HCOOH cis-trans conversion is analyzed by taking into account matrix reorganization and the change of HCOOH position in the cluster. The matrix reorganization is considered within the Debye model of lattice vibrations, whereas the external motion of HCOOH in the cluster is treated using the Einstein model of solids. It has been shown that the literature experimental data on the cis to trans tunneling reaction in the formic acid can be accounted for within the proposed mechanism, which describes the matrix reorganization and the change of the HCOOH position in the noble gas matrix, with fitting parameters of the suggested theoretical model attaining reasonable values.
Dipolar quantum gases and liquids
Pfau, Tilman
Dipolar interactions are fundamentally different from the usual van der Waals forces in real gases. Besides the anisotropy the dipolar interaction is nonlocal and as such allows for self organized structure formation. Candidates for dipolar species are polar molecules, Rydberg atoms and magnetic atoms. More than ten years ago the first dipolar effects in a quantum gas were observed in an ultracold Chromium gas. By the use of a Feshbach resonance a purely dipolar quantum gas was observed three years after. By now dipolar interaction effects have been observed in lattices and also for polar molecules. Recently it became possible to study degenerate gases of lanthanide atoms among which one finds the most magnetic atoms. Similar to the Rosensweig instability in classical magnetic ferrofluids self-organized structure formation was expected. In our experiments with quantum gases of Dysprosium atoms we could recently observe the formation of a droplet crystal. In contrast to theoretical mean field based predictions the superfluid droplets did not collapse. We find that this unexpected stability is due to beyond meanfield quantum corrections of the Lee-Huang-Yang type. We observe and study self-bound droplets which can interfere with each other. These droplets are 100 million times less dense than liquid helium droplets and open new perspectives as a truly isolated quantum system.
Energy-pressure relation for low-dimensional gases
Mancarella, Francesco; Mussardo, Giuseppe; Trombettoni, Andrea
means of ultracold atom set-ups [11-14,17], where bosons are confined within 1d atom waveguides which freeze almost all transverse degrees of freedom [18-20]. The coupling strength of the LL system can be tuned through the Feshbach resonance mechanism [21].Our second paradigmatic example will be the 2d ideal anyonic gases in which we will study the energy-pressure relation in the interpolation between 2d Bose and Fermi gases induced by the pure statistical Aharonov-Bohm interactions. We will consider Abelian and non-Abelian Chern-Simons particle systems, and both models admit a soft-core generalization that can be understood as the result of an additional contact interaction besides the pure statistical one. As it is well known, quantum two-dimensional systems of indistinguishable particles have the peculiarity of admitting generalized braiding statistics, because of the non-trivial topological structure of braiding transformations defined over the space-time ambient manifold. Ordinary bosonic and fermionic quantum statistics in 2d admit the generalization represented by Abelian anyons, where an elementary braiding operation is encoded in terms of a multiplicative phase factor acting on the multi-anyonic scalar wavefunction [22-26]. A different generalization of the standard quantum statistics is represented by non-Abelian anyons, described by a multi-component many-body wavefunction and corresponding to higher-dimensional representations of the braid group: non-Abelian anyons generalize the parastatistics, exactly in the same manner in which Abelian anyons generalize Bose and Fermi statistics.Thermodynamic properties of ideal Abelian anyonic gas (assuming hard-core boundary conditions for the wavefunction at coincident points) were studied in the low-density regime [27]: the exact expression therein obtained for the second virial coefficient is periodic and non-analytic as a function of the statistical parameter. Different approaches have been subsequently used in
Merging of single-particle levels and non-Fermi-liquid behavior of finite Fermi systems
Energy Technology Data Exchange (ETDEWEB)
Khodel, V.A. [Russian Research Centre Kurchatov Institute, Moscow 123182 (Russian Federation); McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States); Clark, J.W.; Li, Haochen [McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States); Zverev, M.V. [Russian Research Centre Kurchatov Institute, Moscow 123182 (Russian Federation)], E-mail: email@example.com
Within the Landau quasiparticle approach, we analyze the possibility of merging of different single-particle levels in finite spherical Fermi systems. It is demonstrated that the opportunity for this behavior is widespread in quantum many-body systems. The salient feature of the phenomenon is the occurrence of nonintegral quasiparticle occupation numbers, leading to a radical alteration of the standard quasiparticle picture. Implications of this alteration are considered for atomic and solid-state systems.
Multiparticle instability in a spin-imbalanced Fermi gas
Whitehead, T. M.; Conduit, G. J.
Weak attractive interactions in a spin-imbalanced Fermi gas induce a multiparticle instability, binding multiple fermions together. The maximum binding energy per particle is achieved when the ratio of the number of up- and down-spin particles in the instability is equal to the ratio of the up- and down-spin densities of states in momentum at the Fermi surfaces, to utilize the variational freedom of all available momentum states. We derive this result using an analytical approach, and verify it using exact diagonalization. The multiparticle instability extends the Cooper pairing instability of balanced Fermi gases to the imbalanced case, and could form the basis of a many-body state, analogously to the construction of the Bardeen-Cooper-Schrieffer theory of superconductivity out of Cooper pairs.
Dai, Liang; Schmidt, Fabian
Fermi Normal Coordinates (FNC) are a useful frame for isolating the locally observable, physical effects of a long-wavelength spacetime perturbation. Their cosmological application, however, is hampered by the fact that they are only valid on scales much smaller than the horizon. We introduce a generalization that we call Conformal Fermi Coordinates (CFC). CFC preserve all the advantages of FNC, but in addition are valid outside the horizon. They allow us to calculate the coupling of long- and short-wavelength modes on all scales larger than the sound horizon of the cosmological fluid, starting from the epoch of inflation until today, by removing the complications of the second order Einstein equations to a large extent, and eliminating all gauge ambiguities. As an application, we present a calculation of the effect of long-wavelength tensor modes on small scale density fluctuations. We recover previous results, but clarify the physical content of the individual contributions in terms of locally measurable ef...
The rapid control of interactions in a two-component Fermi gas
Stites, Ronald William Donald
In this dissertation, we describe a variety of experiments having application to ultra-cold atomic gases. While the majority of the experimental results focus on the development of a novel laser source for cooling and manipulating a gas of fermionic 6Li atoms, we also report on a preliminary investigation of rapidly controlling interactions in a two-component Fermi gas. One of the primary tools for our ultra-cold atomic physics experiments is 671 nm laser light nearly resonant with the D1 and D2 spectroscopic lines of ultracold fermionic 6Li atoms. Traditionally, this light is generated using dye lasers or tapered amplifier systems. Here we describe a diode pumped solid state ring laser system utilizing a Nd:YVO 4 gain crystal. Nd:YVO4 has a 4F 3/2 → 4I13/2 emission line at 1342 nm. This wavelength is double the 671 nm needed for our experiments. As a part of this investigation, we also measured the Verdet constant of undoped Y3Al5O12 in the near infrared for constructing a Faraday rotator used to drive unidirectional operation of our ring laser. As an alternative method to achieve unidirectional, single-frequency operation of the laser, we developed a novel scheme of "self-injection locking" where a small portion of the output beam is coupled back into the cavity to break the symmetry. This technique is useful for high-power, single-frequency operation of a ring laser because lossy elements needed for frequency selection and unidirectional operation of the laser can be removed from the internal cavity. In addition to our laser experiments, we also drive Raman transitions between different magnetic hyperfine states within 6Li atoms. For atoms in the two lowest hyperfine states, there exists a broad Feshbach resonance at 834.1 Gauss whereby the s-wave scattering length diverges, resulting in strong interactions between the two species. By using two phase locked lasers to drive a transition from a strongly interacting state to a weakly interacting state, we can
Tunable topological phases with fermionic atoms in a one-dimensional flux lattice
Deng, Y.; Lü, R.; You, L.
We present a simple scheme for implementing a one-dimensional (1D) magnetic-flux lattice of ultracold fermionic spin-1/2 atoms. The resulting tight-binding model supports gapped and gapless topological phases and chiral currents for Meissner and vortex phases. Its single-particle spectra exhibit topological flat bands at small flux, and the flatness sensitively depends on hopping strength. An effective p -wave interaction arises in a s -wave paired superfluid. Treating atomic internal states as forming a synthetic dimension and balancing the interplay of magnetic flux and Zeeman field, our model describes a tunable topological Fermi superfluid, which paves the way towards experimental explorations of non-Abelian topological matter in 1D atomic quantum gases.
A new look at Thomas–Fermi theory
DEFF Research Database (Denmark)
Solovej, Jan Philip
In this short note, we argue that Thomas–Fermi theory, the simplest of all density functional theories, although failing to explain features such as molecular binding or stability of negative ions, is surprisingly accurate in estimating sizes of atoms. We give both numerical, experimental and rig...
Spin-Seebeck effect in a strongly interacting Fermi gas
Wong, C.H.; Stoof, H.T.C.|info:eu-repo/dai/nl/074851357; Duine, R.A.|info:eu-repo/dai/nl/304830127
We study the spin-Seebeck effect in a strongly interacting, two-component Fermi gas and propose an experiment to measure this effect by relatively displacing spin-up and spin-down atomic clouds in a trap using spin-dependent temperature gradients. We compute the spin-Seebeck coefficient and related
Itinerant Ferromagnetism in a Polarized Two-Component Fermi Gas
DEFF Research Database (Denmark)
Massignan, Pietro; Yu, Zhenhua; Bruun, Georg
We analyze when a repulsively interacting two-component Fermi gas becomes thermodynamically unstable against phase separation. We focus on the strongly polarized limit, where the free energy of the homogeneous mixture can be calculated accurately in terms of well-defined quasiparticles, the repul...... of the minority atoms, raising the prospects of detecting the transition to the elusive itinerant ferromagnetic state with ultracold atoms....
Fermi liquids and Luttinger liquids
Schulz, H. J.; Cuniberti, G.; Pieri, P.
In these lecture notes, the basic physics of Fermi liquids and Luttinger liquids is presented. Fermi liquids are discussed both from a phenomenological viewpoint, in relation to microscopic approaches, and as renormalization group fixed points. Luttinger liquids are introduced using the bosonization formalism, and their essential differences with Fermi liquids are pointed out. Applications to transport effects, the effect of disorder, quantum spin chains, and spin ladders, both insulating and...
Statistical mechanics of a Feshbach-coupled Bose-Fermi gas in an optical lattice
DEFF Research Database (Denmark)
Sørensen, Ole Søe; Nygaard, Nicolai; Blakie, P.B.
We consider an atomic Fermi gas confined in a uniform optical lattice potential, where the atoms can pair into molecules via a magnetic-field-controlled narrow Feshbach resonance. The phase diagram of the resulting atom-molecule mixture in chemical and thermal equilibria is determined numerically...... spectrum with respect to the atomic one for which half of the atoms have been converted into dimers. Importantly we find that the dissociation energy has a nonmonotonic dependence on lattice depth....
Enhancement of soft X-ray emission from fs laser plasma by using mixture of molecule and atomic gases as cluster jet targets and its application for nanostructure imaging
Energy Technology Data Exchange (ETDEWEB)
Pikuz, T A; Faenov, A Ya; Fukuda, Y; Kando, M; Kotaki, H; Daito, I; Homma, T; Kawase, K; Kameshima, T; Kawachi, T; Bolton, P; Daido, H; Kimura, T; Tajima, T; Kato, Y; Bulanov, S V [Kansai Photon Science Institute (KPSI), Japan Atomic Energy Agency (JAEA), Kizugawa-city, Kyoto 619-0215 (Japan); Skobelev, I Yu; Gasilov, S V [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Boldarev, A S; Gasilov, V A, E-mail: firstname.lastname@example.com [Institute for Mathematical Modelling, Russian Academy of Sciences, Moscow (Russian Federation)
Submicron scale clusters, produced by mixture of molecular (CO{sub 2}) and atomic (He) gases expanding from the specifically designed super-sonic nozzle, have been irradiated by femtosecond laser pulses in order to build up a bright debris-free soft X-ray source. Spectroscopy measurements showed that X-ray flux in the strongest oxygen spectral lines (He{sub b}eta at 665.7 eV and L{sub ya}lpha at 653.7 eV) produced by the plasma from gas mixture clusters is 2-8 times larger than in the case of using pure CO{sub 2} or N{sub 2}O clusters as targets and reaches values about 2.8x10{sup 10} ph/(sr centre dot pulse). Lines intensity and spatial dimension were measured from two observation point - along and perpendicular to the laser beam propagation directions. Images of 100 nm thick Mo foils in a wide field of view (cm{sup 2} scale) with high spatial resolution (700 nm) were obtained using LiF crystals as soft X-ray imaging detectors. Agreement between calculated and measured intensity of the image fragment which illustrates overlapping of Mo foil layers confirms accuracy of the plasma parameters measurements.
Atom Skimmers and Atom Lasers Utilizing Them
Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.
Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.
This FERMI multi-chip module contains five million transistors. 25 000 of these modules will handle the flood of information through parts of the ATLAS and CMS detectors at the LHC. To select interesting events for recording, crucial decisions are taken before the data leaves the detector. FERMI modules are being developed at CERN in partnership with European industry.
Fermi Communications and Public Outreach
Cominsky, L
The Sonoma State University (SSU) Education and Public Outreach (E/PO) group participates in the planning and execution of press conferences that feature noteworthy Fermi discoveries, as well as supporting social media and outreach websites. We have also created many scientific illustrations for the media, tools for amateur astronomers for use at star parties, and have given numerous public talks about Fermi discoveries.
Delmastro, Marco
When I settled down to read The Last Man Who Knew Everything by Davis Schwartz, I was asking myself whether there was any need for yet another Enrico Fermi biography. While navigating this ambitious book, I realized that maybe I knew less than I thought about Fermi, and that maybe there was still a lot I could learn.
Photo-Induced Unpinning of Fermi Level in WO3
Directory of Open Access Journals (Sweden)
Steve P. Wilks
Full Text Available Atomic force and high resolution scanning tunneling analyses were carried out onnanostructured WO3 films. It turned out that the band gap measured by scanning tunnelingspectroscopy at surface is lower than the band gap reported in the literature. This effect isattributed to the high density of surface states in this material, which allows tunneling intothese states. Such a high density of surface states pins the Fermi level resulting in modestsurface activity at room temperature. Photo activation of WO3 results in unpinning of theFermi level and thereby in higher chemical activity at surface.
Momentum sharing in imbalanced Fermi systems
Energy Technology Data Exchange (ETDEWEB)
Hen, O.; Sargsian, M.; Weinstein, L. B.; Piasetzky, E.; Hakobyan, H.; Higinbotham, D. W.; Braverman, M.; Brooks, W. K.; Gilad, S.; Adhikari, K. P.; Arrington, J.; Asryan, G.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Beck, A.; Beck, S. M. -T.; Bedlinskiy, I.; Bertozzi, W.; Biselli, A.; Burkert, V. D.; Cao, T.; Carman, D. S.; Celentano, A.; Chandavar, S.; Colaneri, L.; Cole, P. L.; Crede, V.; D' Angelo, A.; De Vita, R.; Deur, A.; Djalali, C.; Doughty, D.; Dugger, M.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Fedotov, G.; Fegan, S.; Forest, T.; Garillon, B.; Garcon, M.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Girod, F. X.; Goetz, J. T.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hanretty, C.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkanov, B. I.; Isupov, E. L.; Jiang, H.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Koirala, S.; Korover, I.; Kuhn, S. E.; Kubarovsky, V.; Lenisa, P.; Levine, W. I.; Livingston, K.; Lowry, M.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mokeev, V.; Movsisyan, A.; Camacho, C. M.; Mustapha, B.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phelps, W.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rizzo, A.; Rosner, G.; Roy, P.; Rossi, P.; Sabatie, F.; Schott, D.; Schumacher, R. A.; Sharabian, Y. G.; Smith, G. D.; Shneor, R.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tkachenko, S.; Ungaro, M.; Vlassov, A. V.; Voutier, E.; Walford, N. K.; Wei, X.; Wood, M. H.; Wood, S. A.; Zachariou, N.; Zana, L.; Zhao, Z. W.; Zheng, X.; Zonta, I.
The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using C-12, Al-27, Fe-56, and Pb-208 targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.
Enrico Fermi Symposium at CERN : opening celebration
CERN. Geneva. Audiovisual Unit
You are cordially invited to the opening celebration on Thursday 12 September at 16:00 (Main Building, Council Chamber), which will include speechs from: Luciano Maiani - Welcome and Introduction Antonino Zichichi - The New 'Centro Enrico Fermi' at Via Panisperna Ugo Amaldi - Fermi at Via Panisperna and the birth of Nuclear Medicine Jack Steinberger - Fermi in Chicago Valentin Telegdi - A Close-up of Fermi Arnaldo Stefanini - Celebrating Fermi's Centenary in Documents and Pictures and the screening of a documentary video about Fermi: Scienziati a Pisa: Enrico Fermi (Scientists at Pisa: Enrico Fermi) created by Francesco Andreotti for La Limonaia from early film, photographs and sound recordings (English version - c. 30 mins).
3D Quantum Hall Effect of Fermi Arc in Topological Semimetals
Wang, C. M.; Sun, Hai-Peng; Lu, Hai-Zhou; Xie, X. C.
The quantum Hall effect is usually observed in 2D systems. We show that the Fermi arcs can give rise to a distinctive 3D quantum Hall effect in topological semimetals. Because of the topological constraint, the Fermi arc at a single surface has an open Fermi surface, which cannot host the quantum Hall effect. Via a "wormhole" tunneling assisted by the Weyl nodes, the Fermi arcs at opposite surfaces can form a complete Fermi loop and support the quantum Hall effect. The edge states of the Fermi arcs show a unique 3D distribution, giving an example of (d -2 )-dimensional boundary states. This is distinctly different from the surface-state quantum Hall effect from a single surface of topological insulator. As the Fermi energy sweeps through the Weyl nodes, the sheet Hall conductivity evolves from the 1 /B dependence to quantized plateaus at the Weyl nodes. This behavior can be realized by tuning gate voltages in a slab of topological semimetal, such as the TaAs family, Cd3 As2 , or Na3Bi . This work will be instructive not only for searching transport signatures of the Fermi arcs but also for exploring novel electron gases in other topological phases of matter.
3D Quantum Hall Effect of Fermi Arcs in Topological Semimetals.
Wang, C M; Sun, Hai-Peng; Lu, Hai-Zhou; Xie, X C
The quantum Hall effect is usually observed in 2D systems. We show that the Fermi arcs can give rise to a distinctive 3D quantum Hall effect in topological semimetals. Because of the topological constraint, the Fermi arc at a single surface has an open Fermi surface, which cannot host the quantum Hall effect. Via a "wormhole" tunneling assisted by the Weyl nodes, the Fermi arcs at opposite surfaces can form a complete Fermi loop and support the quantum Hall effect. The edge states of the Fermi arcs show a unique 3D distribution, giving an example of (d-2)-dimensional boundary states. This is distinctly different from the surface-state quantum Hall effect from a single surface of topological insulator. As the Fermi energy sweeps through the Weyl nodes, the sheet Hall conductivity evolves from the 1/B dependence to quantized plateaus at the Weyl nodes. This behavior can be realized by tuning gate voltages in a slab of topological semimetal, such as the TaAs family, Cd_{3}As_{2}, or Na_{3}Bi. This work will be instructive not only for searching transport signatures of the Fermi arcs but also for exploring novel electron gases in other topological phases of matter.
Directory of Open Access Journals (Sweden)
Ynduráin, Francisco J.
Full Text Available Not available
Los azares de las onomásticas hacen coincidir en este año el centenario del nacimiento de tres de los más grandes físicos del siglo XX. Dos de ellos, Fermi y Heisenberg, dejaron una marca fundamental en la ciencia (ambos, pero sobre todo el segundo y, el primero, también en la tecnología. Lawrence, indudablemente de un nivel inferior al de los otros dos, estuvo sin embargo en el origen de uno de los desarrollos tecnológicos que han sido básicos para la exploración del universo subnuclear en la segunda mitad del siglo que ha terminado hace poco, el de los aceleradores de partículas.
Ultracold atomic quantum gases far from equilibrium
Energy Technology Data Exchange (ETDEWEB)
Gasenzer, Thomas [Institut fuer Theoretische Physik, Ruprecht-Karls Universitaet Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); Berges, Juergen [Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse, 64289 Darmstadt (Germany); Schmidt, Michael G. [Institut fuer Theoretische Physik, Ruprecht-Karls Universitaet Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); Seco, Marcos [Institut fuer Theoretische Physik, Ruprecht-Karls Universitaet Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany)
We calculate the time evolution of a far-from-equilibrium initial state of a non-relativistic ultracold Bose gas in one spatial dimension. The non-perturbative approximation scheme is based on a systematic expansion of the two-particle irreducible effective action in powers of the inverse number of field components. This yields dynamic equations which contain direct scattering, memory and off-shell effects that are not captured in mean-field theory.
Ultracold atomic quantum gases far from equilibrium
Gasenzer, T.; Berges, J.; Schmidt, M G; Seco, M.
We calculate the time evolution of a far-from-equilibrium initial state of a non-relativistic ultracold Bose gas in one spatial dimension. The non-perturbative approximation scheme is based on a systematic expansion of the two-particle irreducible effective action in powers of the inverse number of field components. This yields dynamic equations which contain direct scattering, memory and off-shell effects that are not captured in mean-field theory.
Davisson-Germer Prize Talk: Many-Body Physics with Atomic Fermions
Hulet, Randall
Ultracold atomic gases confined to optical lattices have proven to be highly versatile and tunable systems for realizing novel quantum states of matter. We are using Fermi gases of 6 Li atoms in our laboratory to explore several goals related to the strong correlations that arise in these systems. We have realized the Hubbard model, which has long been suspected of containing the essential ingredients of high temperature superconductivity. We measured the compressibility of the Mott insulating phase that occurs near half filling (1 atom/site), thus demonstrating the excitation gap of the Mott insulator. Progress in this field, however, has been hampered by an inability to cool to low enough temperatures to achieve the most ambitious goals. To address this problem, we have developed the compensated optical lattice method to enable evaporative cooling in the lattice. With this method, we have cooled the Mott insulator sufficiently far to observe short-range antiferromagnetic correlations using Bragg scattering of light. We are currently exploring new methods for entropy storage and redistribution to achieve even lower entropy in the antiferromagnetic phase. Motivated by the enhancement of quantum correlations in low dimensions, we are also exploring Fermi gases in quasi-one-dimension (1D). A deep 2D optical lattice produces an array of 1D tubes which can be weakly coupled by reducing the lattice depth, thus increasing the lattice hopping t between them. We observe a crossover from 1D-like to 3D-like behavior in the phase separation of a spin-imbalanced Fermi gas with increasing t. While this crossover occurs at a value of t that depends on interaction, we find that the crossover location is universally dependent upon the scaled hopping t /ɛb , where ɛb is the pair binding energy. Finally, I will also report progress on measuring the speed of sound of the charge and spin modes in a 1D Fermi gas. Work supported by an ARO MURI, NSF, and the Robert A Welch Foundation.
Gap Solitons of Superfluid Fermi Gas in FS Optical Lattices
Chen, Yan; Zhang, Ke-Zhi; He, Yong-Lin; Liu, Zhen-Lai; Zhu, Liao
By employing the mean-field theory and hydrodynamic scheme, we study the gap solitons of superfluid Fermi gas in Fourier-Synthesized(FS) optical lattices. By means of numerical methods and variational approximation, the atomic interaction, the chemical potential, the potential depth of the lattice and relative phase of the Fermi system are derived along the Bose-Enstein condensation(BEC)side to the Bardeen-Cooper-Schrieffer (BCS)side. It means that the condition exciting gap solitons is obtained. Moreover, we analyze the fundamental gap soltions of the superfluid Fermi gas. It is found that the relative phase α impacts greatly on the properties of fundamental gap solitons for superfluid Fermi gas. Especially, the nonlinearity interaction term g decreases with α. Add, due to Fermi pressure, curvature changes of g in the BEC limit( γ = 1, here, γ is a function of an interaction parameter) is larger than that at unitary ( γ = 2/3). Spatial distribution of gap solitons exhibit very obvious different when the system transit from the BEC side to BCS side.
Nanoclusters and Microparticles in Gases and Vapors
Smirnov, Boris M
Research of processes involving Nanoclusters and Microparticleshas been developing fastin many fields of rescent research, in particular in materials science. To stay at the cutting edge of this development, a sound understanding of the processes is needed. In this work, several processes involving small particles are described, such as transport processes in gases, charging of small particles in gases, chemical processes, atom attachment and quenching of excited atomic particles on surfaces, nucleation, coagulation, coalescence and growth processes for particles and aggregates. This work pres
Merging of single-particle levels and non-Fermi-liquid behavior of finite Fermi systems.
Khodel, V A; Clark, J W; Li, Haochen; Zverev, M V
We examine the problem of finite Fermi systems having a degenerate single-particle spectrum and show that the Landau approach, applied to such a system, admits the possibility of merging single-particle levels. It is demonstrated that the opportunity for this behavior is widespread in quantum many-body systems. The salient feature of the phenomenon is the occurrence of nonintegral quasiparticle occupation numbers, leading to a radical alteration of the standard quasiparticle picture. Implications of this alteration are considered for nuclear, atomic, and solid-state systems.
Rearrangements of interacting Fermi liquids
Yang, Rong-Yao; Jiang, Wei-Zhou
The stability condition of Landau Fermi liquid theory may be broken when the interaction between particles is strong enough. In this case, the ground state is reconstructed to have a particle distribution different from the Fermi-step function. For specific instances, one case with the vector boson exchange and another with the relativistic heavy-ion collision are taken into consideration. With the vector boson exchange, we find that the relative weak interaction strength can lead to the grou...
Conjugate Fermi holes and its manifestation in He-like systems
Energy Technology Data Exchange (ETDEWEB)
Sako, Tokuei, E-mail: email@example.com [Laboratory of Physics, College of Science and Technology, Nihon University, 7-24-1 Narashinodai, Funabashi, 274-8501 Chiba (Japan)
The structure of genuine and conjugate Fermi holes in two-electron atomic systems, namely He and He-like atomic ions, has been studied relying on accurate full configuration interaction wave functions. The standard Fermi hole exists in the vicinity of region in the two-electron coordinate space satisfying the well-known condition, r{sub 1} = r{sub 2}, while the conjugate Fermi hole exists in the vicinity of region close to this genuine Fermi hole but satisfying r{sub 1} ≠ r{sub 2} instead of r{sub 1} = r{sub 2}. Existence of these holes has shown to give an insightful interpretation of the origin of the first Hund rule and of the anomalously strong angular correlation manifested in the series of the singlet-triplet pair of singly-excited states of the aforementioned systems.
Strength of metals at the Fermi length scale
Energy Technology Data Exchange (ETDEWEB)
Armstrong, Jason N.; Hua, Susan Z.; Chopra, Harsh Deep [Laboratory for Quantum Devices, Materials Program, Mechanical and Aerospace Engineering Department, The State University of New York at Buffalo, Buffalo, NY (United States)
Using silver and gold, we have measured the size-dependence of the yield strength of atomic-sized samples as small as a single-atom bridge, with pico-level resolution in the applied force and displacement. The strength approaches theoretical values as the diameter of the sample becomes comparable to the Fermi wavelength of electrons ({proportional_to}0.5 nm); in the limit of a single-atom bridge, the strength is over four orders of magnitude higher than in bulk single crystals. Results provide direct evidence for Pauling's prediction of bond stiffening with reduced atomic coordination. Beginning with a single-atom bridge, strength evolves in a staircase manner in Ag, instead of the intuitively assumed continuous approach to a saturating bulk value. Measured strength approaching theoretical (ideal) values at the Fermi length scale, corresponding to a sample made of a single-atom Au bridge. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Charge distribution and Fermi level in bimetallic nanoparticles
Holmberg, Nico; Laasonen, Kari; Peljo, Pekka Eero
Upon metal-metal contact, a transfer of electrons will occur between the metals until the Fermi levels in both phases are equal, resulting in a net charge difference across the metal-metal interface. Here, we have examined this contact electrification in bimetallic model systems composed of mixed Au-Ag nanoparticles containing ca. 600 atoms using density functional theory calculations. We present a new model to explain this charge transfer by considering the bimetallic system as a nanocapacit...
Optical setup for two-colour experiments at the low density matter beamline of FERMI
Finetti, Paola; Demidovich, Alexander; Plekan, Oksana; Di Fraia, Michele; Cucini, Riccardo; Callegari, Carlo; Cinquegrana, Paolo; Sigalotti, Paolo; Ivanov, Rosen; Danailov, Miltcho B.; Fava, Claudio; De Ninno, Giovanni; Coreno, Marcello; Grazioli, Cesare; Feifel, Raimund; Squibb, Richard J.; Mazza, Tommaso; Meyer, Michael; Prince, Kevin C.
The low density matter beamline of the free electron laser facility FERMI is dedicated to the study of atomic, molecular and cluster systems, and here we describe the optical setup available for two-colour experiments. Samples can be exposed to ultrashort pulses from a Ti:Sapphire source (fundamental, or second or third harmonic), and ultrashort light pulses of FERMI in the EUV/soft x-ray region with a well-defined temporal delay, and negligible jitter (space.
Relativistic Scott correction for atoms and molecules
DEFF Research Database (Denmark)
Solovej, Jan Philip; Sørensen, Thomas Østergaard; Spitzer, Wolfgang Ludwig
We prove the first correction to the leading Thomas-Fermi energy for the ground state energy of atoms and molecules in a model where the kinetic energy of the electrons is treated relativistically. The leading Thomas-Fermi energy, established in [25], as well as the correction given here, are of ......We prove the first correction to the leading Thomas-Fermi energy for the ground state energy of atoms and molecules in a model where the kinetic energy of the electrons is treated relativistically. The leading Thomas-Fermi energy, established in [25], as well as the correction given here......, are of semiclassical nature. Our result on atoms and molecules is proved from a general semiclassical estimate for relativistic operators with potentials with Coulomb-like singularities. This semiclassical estimate is obtained using the coherent state calculus introduced in [36]. The paper contains a unified treatment...
Fluctuations of Imbalanced Fermionic Superfluids in Two Dimensions Induce Continuous Quantum Phase Transitions and Non-Fermi-Liquid Behavior
Directory of Open Access Journals (Sweden)
Philipp Strack
Full Text Available We study the nature of superfluid pairing in imbalanced Fermi mixtures in two spatial dimensions. We present evidence that the combined effect of Fermi surface mismatch and order parameter fluctuations of the superfluid condensate can lead to continuous quantum phase transitions from a normal Fermi mixture to an intermediate Sarma-Liu-Wilczek superfluid with two gapless Fermi surfaces—even when mean-field theory (incorrectly predicts a first-order transition to a phase-separated "Bardeen-Cooper-Schrieffer plus excess fermions" ground state. We propose a mechanism for non-Fermi-liquid behavior from repeated scattering processes between the two Fermi surfaces and fluctuating Cooper pairs. Prospects for experimental observation with ultracold atoms are discussed.
7th International Fermi Symposium
The two Fermi instruments have been surveying the high-energy sky since August 2008. The Large Area Telescope (LAT) has discovered more than three thousand gamma-ray sources and many new source classes, bringing the importance of gamma-ray astrophysics to an ever-broadening community. The LAT catalog includes supernova remnants, pulsar wind nebulae, pulsars, binary systems, novae, several classes of active galaxies, starburst galaxies, normal galaxies, and a large number of unidentified sources. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from a wide range of transients. Fermi LAT's study of diffuse gamma-ray emission in our Galaxy revealed giant bubbles, as well as an excess of gamma-rays from the Galactic center region, both observations have become exciting puzzles for the astrophysics community. The direct measurement of a harder-than- expected cosmic-ray electron spectrum may imply the presence of nearby cosmic-ray accelerators. LAT data have provided stringent constraints on new phenomena such as supersymmetric dark-matter annihilations as well as tests of fundamental physics. The full reprocessing of the entire mission dataset with Pass 8 includes improved event reconstruction, a wider energy range, better energy measurements, and significantly increased effective area, all them boosting the discovery potential and the ability to do precision observations with LAT. The Gamma-ray Burst Monitor (GBM) continues to be a prolific detector of gamma-ray transients: magnetars, solar flares, terrestrial gamma-ray flashes and gamma-ray bursts at keV to MeV energies, complementing the higher energy LAT observations of those sources in addition to providing valuable science return in their own right. All gamma-ray data are made immediately available at the Fermi Science Support Center (http://fermi.gsfc.nasa.gov/ssc). These publicly available data and Fermi analysis tools have enabled a large number of important studies. We
On the Dynamics of the Fermi-Bose Model
DEFF Research Database (Denmark)
Ögren, Magnus; Carlsson, M.
can be used for studies of three-dimensional physical systems of arbitrary geometry. We illustrate the generality of our approach by giving numerical results for the dynamics of Glauber type atomic pair correlation functions for a non-isotropic three-dimensional harmonically trapped molecular Bose-Einstein......We consider the exponential matrix representing the dynamics of the Fermi-Bose model in an undepleted bosonic field approximation. A recent application of this model is molecular dimers dissociating into its atomic compounds. The problem is solved in D spatial dimensions by dividing the system...... condensate....
The Fermiac or Fermi's Trolley
Coccetti, F.
The Fermiac, known also as Fermi's trolley or Monte Carlo trolley, is an analog computer used to determine the change in time of the neutron population in a nuclear device, via the Monte Carlo method. It was invented by Enrico Fermi and constructed by Percy King at Los Alamos in 1947, and used for about two years. A replica of the Fermiac was built at INFN mechanical workshops of Bologna in 2015, on behalf of the Museo Storico della Fisica e Centro Studi e Ricerche "Enrico Fermi", thanks to the original drawings made available by Los Alamos National Laboratory (LANL). This reproduction of the Fermiac was put in use, and a simulation was developed.
Novel behavior of monolayer quantum gases on graphene, graphane and fluorographene.
Reatto, Luciano; Galli, Davide E; Nava, Marco; Cole, Milton W
This article discusses the behavior of submonolayer quantum films (He and H2) on graphene and newly discovered surfaces that are derived from graphene. Among these substrates are graphane (abbreviated GH), which has an H atom bonded to each C atom, and fluorographene (GF). The subject is introduced by describing the related problem of monolayer films on graphite. For that case, extensive experimental and theoretical investigations have revealed that the phase diagrams of the Bose gases (4)He and para-H2 are qualitatively similar, differing primarily in a higher characteristic temperature scale for H2 than for He. The phase behavior of these films on one side of pristine graphene, or both sides of free-standing graphene, is expected to be similar to that on graphite. We point out the possibility of novel phenomena in adsorption on graphene related to the large flexibility of the graphene sheet, to the non-negligible interaction between atoms adsorbed on opposite sides of the sheet and to the perturbation effect of the adsorbed layer on the Dirac electrons. In contrast, the behavior predicted on GF and GH surfaces is very different from that on graphite, a result of the different corrugation, i.e., the lateral variation of the potential experienced by these gases. This arises because on GF, for example, half of the F atoms are located above the C plane while the other half are below this plane. Hence, the He and H2 gases experience very different potentials from those on graphite or graphene. As a result of this novel geometry and potential, distinct properties are observed. For example, the (4)He film's ground state on graphite is a two-dimensional (2D) crystal commensurate with the substrate, the famous [Formula: see text] phase; on GF and GH, instead, it is predicted to be an anisotropic superfluid. On GF the anisotropy is so extreme that the roton excitations are very anisotropic, as if the bosons are moving in a multiconnected space along the bonds of a
Absorption imaging of ultracold atoms on atom chips
DEFF Research Database (Denmark)
Smith, David A.; Aigner, Simon; Hofferberth, Sebastian
Imaging ultracold atomic gases close to surfaces is an important tool for the detailed analysis of experiments carried out using atom chips. We describe the critical factors that need be considered, especially when the imaging beam is purposely reflected from the surface. In particular we present...... methods to measure the atom-surface distance, which is a prerequisite for magnetic field imaging and studies of atom surface-interactions....
The Fermi Paradox is Neither Fermis Nor a Paradox
Gray, Robert H
The so-called Fermi paradox claims that if technological life existed anywhere else, we would see evidence of its visits to Earth-and since we do not, such life does not exist, or some special explanation is needed. Enrico Fermi, however, never published anything on this topic. On the one occasion he is known to have mentioned it, he asked 'where is everybody?'- apparently suggesting that we don't see extraterrestrials on Earth because interstellar travel may not be feasible, but not suggesting that intelligent extraterrestrial life does not exist, or suggesting its absence is paradoxical. The claim 'they are not here; therefore they do not exist' was first published by Michael Hart, claiming that interstellar travel and colonization of the galaxy would be inevitable if intelligent extraterrestrial life existed, and taking its absence here as proof that it does not exist anywhere. The Fermi paradox appears to originate in Hart's argument, not Fermi's question. Clarifying the origin of these ideas is important...
Method and system for continuous atomic layer deposition
Energy Technology Data Exchange (ETDEWEB)
Elam, Jeffrey W.; Yanguas-Gil, Angel; Libera, Joseph A.
A system and method for continuous atomic layer deposition. The system and method includes a housing, a moving bed which passes through the housing, a plurality of precursor gases and associated input ports and the amount of precursor gases, position of the input ports, and relative velocity of the moving bed and carrier gases enabling exhaustion of the precursor gases at available reaction sites.
Recognizing nitrogen dopant atoms in graphene using atomic force microscopy
DEFF Research Database (Denmark)
van der Heijden, Nadine J.; Smith, Daniel; Calogero, Gaetano
Doping graphene by heteroatoms such as nitrogen presents an attractive route to control the position of the Fermi level in the material. We prepared N-doped graphene on Cu(111) and Ir(111) surfaces via chemical vapor deposition of two different molecules. Using scanning tunneling microscopy images...... as a benchmark, we show that the position of the dopant atoms can be determined using atomic force microscopy. Specifically, the frequency shift-distance curves Delta f(z) acquired above a N atom are significantly different from the curves measured over a C atom. Similar behavior was found for N-doped graphene...
Schoen, Helmut
Technical gases are used in almost every field of industry, science and medicine and also as a means of control by government authorities and institutions and are regarded as indispensable means of assistance. In this complete handbook of purified gases the physical foundations of purified gases and mixtures as well as their manufacturing, purification, analysis, storage, handling and transport are presented in a comprehensive way. This important reference work is accompanied with a large number of Data Sheets dedicated to the most important purified gases.
Tomkins, RPT
This volume contains tabulated collections and critical evaluations of original data for the solubility of gases in molten salts, gathered from chemical literature through to the end of 1989. Within the volume, material is arranged according to the individual gas. The gases include hydrogen halides, inert gases, oxygen, nitrogen, hydrogen, carbon dioxide, water vapor and halogens. The molten salts consist of single salts, binary mixtures and multicomponent systems. Included also, is a special section on the solubility of gases in molten silicate systems, focussing on slags and fluxes.
STEM education and Fermi problems
Holubova, Renata
One of the research areas of Physics education is the study of the educational process. Investigations in this area are aimed for example on the teaching and learning process and its results. The conception of STEM education (Science, Technology, Engineering, and Mathematics) is discussed - it is one possible approach to the preparation of the curriculum and the focus on the educational process at basic and secondary schools. At schools in the Czech Republic STEM is much more realized by the application of interdisciplinary relations between subjects Physics-Nature-Technique. In both conceptions the aim is to support pupils' creativity, critical thinking, cross-curricular links. In this context the possibility of using Fermi problems in teaching Physics was discussed (as an interdisciplinary and constructivist activity). The aim of our research was the analysis of Fermi problems solving strategies, the ability of pupils to solve Fermi problems. The outcome of our analysis was to find out methods and teaching strategies which are important to use in teaching - how to solve qualitative and interdisciplinary tasks in physics. In this paper the theoretical basis of STEM education and Fermi problems will be presented. The outcome of our findings based on the research activities will be discussed so as our experiences from 10 years of Fermi problems competition that takes place at the Science Faculty, Palacky University in Olomouc. Changes in competencies of solving tasks by our students (from the point of view in terms of modern, activating teaching methods recommended by theory of Physics education and other science subjects) will be identified.
Atmospheric spatial atomic-layer-deposition of Zn(O, S) buffer layer for flexible Cu(In, Ga)Se2 solar cells: From lab-scale to large area roll to roll processing
Frijters, C.H.; Bolt, P.J.; Poodt, P.W.G.; Knaapen, R.; Brink, J. van den; Ruth, M.; Bremaud, D.; Illiberi, A.
In this manuscript we present the first successful application of a spatial atomic-layer-deposition process to thin film solar cells. Zn(O,S) has been grown by spatial atomic layer deposition (S-ALD) at atmospheric pressure and applied as buffer layer in rigid and flexible CIGS cells by a lab-scale
Noble gases in pure lipid membranes.
Sierra-Valdez, F J; Ruiz-Suárez, J C
The mechanism of how a noble gas modifies the excitability of nerve cells and how such excitability can be recovered under hyperbaric pressure remains unclear. Here we present a calorimetric study where the melting point depression of pure lipid membranes induced by noble gases and its recovery with a hydrostatic pressure is addressed. A correlation is found between the electric polarizability (α) of these gases and their effect on the melting transition of the membranes. These results concur with other findings to support the idea that general anesthesia only depends on the ability of a certain atom or molecule to increase the general disorder of the membrane.
Equilibrium Molecular Interactions in Pure Gases
Directory of Open Access Journals (Sweden)
Boris I. Sedunov
Full Text Available The equilibrium molecular interactions in pure real gases are investigated based on the chemical thermodynamics principles. The parallels between clusters in real gases and chemical compounds in equilibrium media have been used to improve understanding of the real gas structure. A new approach to the equilibrium constants for the cluster fractions and new methods to compute them and their significant parameters from the experimental thermophysical data are developed. These methods have been applied to some real gases, such as Argon and Water vapors and gaseous Alkanes. It is shown that the four-particle clusters make a noticeable contribution in the thermophysical properties of the equilibrium Water vapor. It is shown also that the effective bond energy for dimers in Alkanes linearly grows with the number of carbon atoms in the molecule.
Fermi Timing and Synchronization System
Energy Technology Data Exchange (ETDEWEB)
Wilcox, R.; Staples, J.; Doolittle, L.; Byrd, J.; Ratti, A.; Kaertner, F.X.; Kim, J.; Chen, J.; Ilday, F.O.; Ludwig, F.; Winter, A.; Ferianis, M.; Danailov, M.; D' Auria, G.
The Fermi FEL will depend critically on precise timing of its RF, laser and diagnostic subsystems. The timing subsystem to coordinate these functions will need to reliably maintain sub-100fs synchronicity between distant points up to 300m apart in the Fermi facility. The technology to do this is not commercially available, and has not been experimentally demonstrated in a working facility. Therefore, new technology must be developed to meet these needs. Two approaches have been researched by different groups working with the Fermi staff. At MIT, a pulse transmission scheme has been developed for synchronization of RF and laser devices. And at LBL, a CW transmission scheme has been developed for RF and laser synchronization. These respective schemes have advantages and disadvantages that will become better understood in coming years. This document presents the work done by both teams, and suggests a possible system design which integrates them both. The integrated system design provides an example of how choices can be made between the different approaches without significantly changing the basic infrastructure of the system. Overall system issues common to any synchronization scheme are also discussed.
A Fermi-degenerate three-dimensional optical lattice clock
Campbell, S. L.; Hutson, R. B.; Marti, G. E.; Goban, A.; Darkwah Oppong, N.; McNally, R. L.; Sonderhouse, L.; Robinson, J. M.; Zhang, W.; Bloom, B. J.; Ye, J.
Strontium optical lattice clocks have the potential to simultaneously interrogate millions of atoms with a high spectroscopic quality factor of 4 × 1017. Previously, atomic interactions have forced a compromise between clock stability, which benefits from a large number of atoms, and accuracy, which suffers from density-dependent frequency shifts. Here we demonstrate a scalable solution that takes advantage of the high, correlated density of a degenerate Fermi gas in a three-dimensional (3D) optical lattice to guard against on-site interaction shifts. We show that contact interactions are resolved so that their contribution to clock shifts is orders of magnitude lower than in previous experiments. A synchronous clock comparison between two regions of the 3D lattice yields a measurement precision of 5 × 10-19 in 1 hour of averaging time.
Thermodynamics, Gibbs Method and Statistical Physics of Electron Gases Gibbs Method and Statistical Physics of Electron Gases
Askerov, Bahram M
This book deals with theoretical thermodynamics and the statistical physics of electron and particle gases. While treating the laws of thermodynamics from both classical and quantum theoretical viewpoints, it posits that the basis of the statistical theory of macroscopic properties of a system is the microcanonical distribution of isolated systems, from which all canonical distributions stem. To calculate the free energy, the Gibbs method is applied to ideal and non-ideal gases, and also to a crystalline solid. Considerable attention is paid to the Fermi-Dirac and Bose-Einstein quantum statistics and its application to different quantum gases, and electron gas in both metals and semiconductors is considered in a nonequilibrium state. A separate chapter treats the statistical theory of thermodynamic properties of an electron gas in a quantizing magnetic field.
... LDL Particle Testing (LDL-P) Lead Legionella Testing Leptin Levetiracetam Lipase Lipid Profile Lipoprotein (a) Lithium Liver ... such as asthma or chronic obstructive pulmonary disease (COPD) is suspected. Blood gases may also be used ...
National Research Council Canada - National Science Library
Jacques Arnaud; Laurent Chusseau; Fabrice Philippe
We show that the thermodynamics of ideal gases may be derived solely from the Democritean concept of corpuscles moving in vacuum plus a principle of simplicity, namely that these laws are independent...
Kauzmann, Walter
Monograph and text supplement for first-year students of physical chemistry focuses chiefly on the molecular basis of important thermodynamic properties of gases, including pressure, temperature, and thermal energy. 1966 edition.
Non-Fermi-liquid behavior of strongly correlated Fermi systems explained by the Fermi-liquid approach
Energy Technology Data Exchange (ETDEWEB)
Khodel, V.A. [Russian Research Centre Kurchatov Institute, Moscow 123182 (Russian Federation); McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States)], E-mail: firstname.lastname@example.com; Clark, J.W. [McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States); Yakovenko, V.M. [University of Maryland, College Park, MA 20742-4111 (United States); Zverev, M.V. [Russian Research Centre Kurchatov Institute, Moscow 123182 (Russian Federation)
Non-Fermi-liquid behavior of strongly correlated Fermi systems is derived within the Landau approach. We attribute this behavior to a phase transition associated with a rearrangement of the Landau state that leads to flattening of a portion of the single-particle spectrum in the vicinity of the Fermi surface. We demonstrate that the quasiparticle subsystem responsible for the flat spectrum possesses the same thermodynamic properties as a gas of localized spins. Theoretical results compare favorably with available experimental data.
Fermi surfaces, Fermi patches, and Fermi arcs in high T{sub c} superconductors.
Energy Technology Data Exchange (ETDEWEB)
Norman, M. R.
A defining property of metals is the existence of a Fermi surface: for two dimensions, a continuous contour in momentum space which separates occupied from unoccupied states. In this paper, I discuss angle resolved photoemission data on the cuprate superconductor BSCCO and argue that it is not best thought of in this conventional picture. Rather, the data are consistent with patches of finite area connected by more conventional arcs. Novel physics is associated with the patches, in that the states contained in a patch are dispersionless and thus interaction dominated. In the pseudogap phase, the patches are gapped out, leaving the Fermi arcs disconnected. This unusual situation may be the key to understanding the microscopic physics of the high temperature superconductors, in that the pairing correlations are strongest in the patches, yet the superfluid density lives only on the arcs.
Physics Utilizing Spin-Polarized Gases
National Research Council Canada - National Science Library
Happer, W
.... A very important consideration in the use of laser-polarized 3He and 129Xe is that the nuclear spins of these gases do not relax at the surface of the container in which they are pumped or stored. This research has shown that in the case of 129Xe in cells with polymer wall coatings, much of the relaxation is due to unusually long trapping of the 129Xe atoms at sites surrounded by protons in the polymer.
Origin of inertia in large-amplitude collective motion in finite Fermi ...
Indian Academy of Sciences (India)
Origin of inertia in large-amplitude collective motion in finite Fermi systems. SUDHIR R JAIN. Nuclear Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India. E-mail: firstname.lastname@example.com. MS received 6 January 2011; revised 27 July 2011; accepted 26 August 2011. Abstract. We argue that mass ...
The Low Density Matter (LDM) beamline at FERMI: optical layout and first commissioning.
Svetina, Cristian; Grazioli, Cesare; Mahne, Nicola; Raimondi, Lorenzo; Fava, Claudio; Zangrando, Marco; Gerusina, Simone; Alagia, Michele; Avaldi, Lorenzo; Cautero, Giuseppe; de Simone, Monica; Devetta, Michele; Di Fraia, Michele; Drabbels, Marcel; Feyer, Vitaliy; Finetti, Paola; Katzy, Raphael; Kivimäki, Antti; Lyamayev, Viktor; Mazza, Tommaso; Moise, Angelica; Möller, Thomas; O'Keeffe, Patrick; Ovcharenko, Yevheniy; Piseri, Paolo; Plekan, Oksana; Prince, Kevin C; Sergo, Rudi; Stienkemeier, Frank; Stranges, Stefano; Coreno, Marcello; Callegari, Carlo
The Low Density Matter (LDM) beamline has been built as part of the FERMI free-electron laser (FEL) facility to serve the atomic, molecular and cluster physics community. After the commissioning phase, it received the first external users at the end of 2012. The design and characterization of the LDM photon transport system is described, detailing the optical components of the beamline.
[The Effects of Complex of Benzoquinone on Fermi Resonance].
Li, Shuai-peng; Zhang, Feng-qin; Jiang, Li-tong; Lin, Xiao-long; Jiang, Yong-heng; Zhang Liu-yang; Lin, Bo; Gu, Hao
Fermi resonance phenomenon exists in simple compounds and it also widely exists in vibration spectra of complex. The complex can be formed by adding up simple compounds. As a result, the characteristic parameters of some parts of molecule will make changes, and the molecular spectra have a significant change along with it. Benzoquinone and proline in the solution form charge-transfer complex under certain conditions, but the spectra intensity is weak, our research uses Teflon liquid-core optical fiber technology to gain high quality resonance Raman spectra. We acquire Raman spectra of Benzoquinone and its complex in experiments, and analyze the characteristic parameters of Fermi resonance according to J. F. Bertran quantum theory. The results shows that, because of the formation of complex, Fermi resonance peak of C==0 bond shifts to high wavelength, the spectra intensity decreases, the frequency space increases, the coupling coefficient increases. The explanation is that, in the solution of complex, proline is donor, while benzoquinone is acceptor, the non-bonding electron of N atom which is belong to proline transfers to the pi anti-bonding orbital of benzoquinone, then n-pi* charge transfer complex is produced. That causes the change of molecular energy level, changes the Raman spectra. All these researches provide new idea and clue for spectral line certification and attribution of complex molecules, complexes and polymer.
Friedrich, Harald
This expanded and updated well-established textbook contains an advanced presentation of quantum mechanics adapted to the requirements of modern atomic physics. It includes topics of current interest such as semiclassical theory, chaos, atom optics and Bose-Einstein condensation in atomic gases. In order to facilitate the consolidation of the material covered, various problems are included, together with complete solutions. The emphasis on theory enables the reader to appreciate the fundamental assumptions underlying standard theoretical constructs and to embark on independent research projects. The fourth edition of Theoretical Atomic Physics contains an updated treatment of the sections involving scattering theory and near-threshold phenomena manifest in the behaviour of cold atoms (and molecules). Special attention is given to the quantization of weakly bound states just below the continuum threshold and to low-energy scattering and quantum reflection just above. Particular emphasis is laid on the fundamen...
Spin-orbit-coupled quantum gases
Radic, Juraj
The dissertation explores the effects of synthetic spin-orbit coupling on the behaviour of quantum gases in several different contexts. We first study realistic methods to create vortices in spin-orbit-coupled (SOC) Bose-Einstein condensates (BEC). We propose two different methods to induce thermodynamically stable static vortex configurations: (1) to rotate both the Raman lasers and the anisotropic trap; and (2) to impose a synthetic Abelian field on top of synthetic spin-orbit interactions. We solve the Gross-Pitaevskii equation for several experimentally relevant regimes and find new interesting effects such as spatial separation of left- and right-moving spin-orbit-coupled condensates, and the appearance of unusual vortex arrangements. Next we consider cold atoms in an optical lattice with synthetic SOC in the Mott-insulator regime. We calculate the parameters of the corresponding tight-binding model and derive the low-energy spin Hamiltonian which is a combination of Heisenberg model, quantum compass model and Dzyaloshinskii-Moriya interaction. We find that the Hamiltonian supports a rich classical phase diagram with collinear, spiral and vortex phases. Next we study the time evolution of the magnetization in a Rashba spin-orbit-coupled Fermi gas, starting from a fully-polarized initial state. We model the dynamics using a Boltzmann equation, which we solve in the Hartree-Fock approximation. The resulting non-linear system of equations gives rise to three distinct dynamical regimes controlled by the ratio of interaction and spin-orbit-coupling strength lambda: for small lambda, the magnetization decays to zero. For intermediate lambda, it displays undamped oscillations about zero and for large lambda, a partially magnetized state is dynamically stabilized. Motivated by an interesting stripe phase which appears in BEC with SOC [Li et al., Phys. Rev. Lett. 108, 225301 (2011)], we study the finite-temperature phase diagram of a pseudospin-1/2 Bose gas with
Zahnle, Kevin
An overview of the history and current status of research on planetary noble gases is presented. The discovery that neon and argon are vastly more abundant on Venus than on earth points to the solar wind rather than condensation as the fundamental process for placing noble gases in the atmospheres of the terrestrial planets; however, solar wind implantation may not be able to fully reproduce the observed gradient, nor does it obviously account for similar planetary Ne/Ar ratios and dissimilar planetary Ar/Kr ratios. More recent studies have emphasized escape rather than accretion. Hydrodynamic escape, which is fractionating, readily accounts for the difference between atmospheric neon and isotopically light mantle neon. Atmospheric cratering, which is nearly nonfractionating, can account for the extreme scarcity of nonradiogenic noble gases (and other volatiles) on Mars.
Fermi condensates for dynamic imaging of electromagnetic fields.
Koponen, T K; Pasanen, J; Törmä, P
Ultracold gases provide micrometer size samples whose sensitivity to external fields may be exploited in sensor applications. Bose-Einstein condensates of atomic gases have been demonstrated to perform excellently as magnetic field sensors in atom chips. Here we propose that condensates of fermions can be used for noninvasive sensing of time-dependent and static magnetic and electric fields, by utilizing the tunable energy gap in the excitation spectrum as a frequency filter. Perturbations by the field create collective excitations and quasiparticles. The latter requires the frequency of the perturbation to exceed the gap. The frequencies of the field may be selectively monitored from the amount of quasiparticles which is measurable, e.g., by rf spectroscopy. We analyze the method by calculating the density-density susceptibility and discuss its sensitivity and spatial resolution.
The relativistic Scott correction for atoms and molecules
DEFF Research Database (Denmark)
Solovej, Jan Philip; Sørensen, Thomas Østergaard; Spitzer, Wolfgang L.
We prove the first correction to the leading Thomas-Fermi energy for the ground state energy of atoms and molecules in a model where the kinetic energy of the electrons is treated relativistically. The leading Thomas-Fermi energy, established in [25], as well as the correction given here are of s......We prove the first correction to the leading Thomas-Fermi energy for the ground state energy of atoms and molecules in a model where the kinetic energy of the electrons is treated relativistically. The leading Thomas-Fermi energy, established in [25], as well as the correction given here...... are of semi-classical nature. Our result on atoms and molecules is proved from a general semi-classical estimate for relativistic operators with potentials with Coulomb-like singularities. This semi-classical estimate is obtained using the coherent state calculus introduced in [36]. The paper contains...
Shear viscosity in an anisotropic unitary Fermi gas
Samanta, Rickmoy; Sharma, Rishi; Trivedi, Sandip P.
We consider a system consisting of a strongly interacting, ultracold unitary Fermi gas under harmonic confinement. Our analysis suggests the possibility of experimentally studying, in this system, an anisotropic shear viscosity tensor driven by the anisotropy in the trapping potential. In particular, we suggest that this experimental setup could mimic some features of anisotropic geometries that have recently been studied for strongly coupled field theories which have a dual gravitational description. Results using the AdS/CFT (anti-de Sitter/conformal field theory correspondence) in these theories show that in systems with a background linear potential, certain viscosity components can be made much smaller than the entropy density, parametrically violating the bound proposed by Kovtun, Son, and Starinets (KSS). This intuition, along with results from a Boltzmann analysis that we perform, suggests that a violation of the KSS bound can perhaps occur in the unitary Fermi gas system when it is subjected to a suitable anisotropic trapping potential which may be approximated to be linear in a suitable range of parameters. We give a concrete proposal for an experimental setup where an anisotropic shear viscosity tensor may arise. In such situations, it may also be possible to observe a reduction in the spin-1 component of the shear viscosity from its lowest value observed so far in ultracold Fermi gases. In extreme anisotropic situations, the reduction may be enough to reduce the shear viscosity to entropy ratio below the proposed KSS bound, although this regime is difficult to analyze in a theoretically controlled manner.
Fermi and the Art of Estimation
Indian Academy of Sciences (India)
IAS Admin
Fermi and the Art of Estimation. Rajaram Nityananda. Keywords. Fermi estimate, order of magni- tude, dimensional analysis. Rajaram Nityananda worked at the Raman. Research Institute in. Bangalore and the. National Centre for. Radio Astrophysics in. Pune, and has now started teaching at the. Indian Institute for.
Enrico Fermi significato di una scoperta
Questo volume è la riedizione, rinnovata ed ampliata, del volume "Enrico Fermi. Significato di una scoperta" edito dal FIEN (Forum Italiano dell'Energia Nucleare) nel 1982 e nel 1992 in occasione, rispettivamente, del 40mo e del 50mo anniversario della pila di Fermi.
Fermi and the Theory of Weak Interactions
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 1. Fermi and the Theory of Weak Interactions. G Rajasekaran. General Article Volume 19 Issue 1 January 2014 pp 18-44 ... Keywords. Fermi; beta decay; parity violation; electroweak theory; neutral current; quarks and leptons; neutrino mass.
Annealing, lattice disorder and non-Fermi liquid behavior in UCu4Pd
Energy Technology Data Exchange (ETDEWEB)
Booth, C.H.; Scheidt, E.-W.; Killer, U.; Weber, A.; Kehrein, S.
The magnetic and electronic properties of non-Fermi liquid UCu{sub 4Pd} depend on annealing conditions. Local structural changes due to this annealing are reported from UL{sub III}- and Pd K-edge x-ray absorption fine-structure measurements. In particular, annealing decreases the fraction of Pd atoms on nominally Cu 16e sites and the U-Cu pair-distance distribution width. This study provides quantitative information on the amount of disorder in UCu{sub 4Pd} and allows an assessment of its possible importance to the observed non-Fermi liquid behavior.
PREFACE: Fermi surface analysis using surface methods
Michel, E. G.
The Fermi surface of a crystalline solid represents a paradigm of quantum solid state physics: its shape is dictated by quantum mechanics, by the Fermi-Dirac statistics for electrons and by the character of Bloch states in solids. Most physical observables depend in one or other way on the shape of the Fermi surface. Due these reasons, the Fermi surface of solids has been investigated since more than 50 years using different techniques, the most important ones being the de Haas-van Alphen effect and Compton scattering. These techniques probe very precisely the Fermi surface of crystalline solids, but surface sensitive techniques are advantageous whenever no large single-crystalline samples are available, if the Brillouin zone is small or if the surface is significantly modified. In the case of low-dimensional materials, only surface sensitive techniques can be used to analyze the Fermi surface. Angle-resolved photoemission is the most powerful surface technique able to probe the Fermi surface of a solid or a surface. Also scanning tunnelling microscopy provides information on the Fermi surface, under favourable conditions. This special section presents a collection of nine invited review articles on the application of these two techniques to the study of the Fermi surface. The first paper by Kurtz reviews some general aspects on the measurement of a Fermi surface using photoemission. The next three articles deal with the Fermi surface of bulk materials. The case of a charge density wave material, where the Fermi surface is expected to play a crucial role in the stability of a particular phase, is considered in the paper by Aebi. Takahashi analyzes the electronic structure and Fermi surface of boride superconductors. Finally, Ding presents a study on how doping affects the Fermi surface of cobaltates and its relationship with other properties of these materials. The next four articles consider different examples of the application of angle-resolved photoemission to
Nuclear physics. Momentum sharing in imbalanced Fermi systems.
Hen, O; Sargsian, M; Weinstein, L B; Piasetzky, E; Hakobyan, H; Higinbotham, D W; Braverman, M; Brooks, W K; Gilad, S; Adhikari, K P; Arrington, J; Asryan, G; Avakian, H; Ball, J; Baltzell, N A; Battaglieri, M; Beck, A; May-Tal Beck, S; Bedlinskiy, I; Bertozzi, W; Biselli, A; Burkert, V D; Cao, T; Carman, D S; Celentano, A; Chandavar, S; Colaneri, L; Cole, P L; Crede, V; D'Angelo, A; De Vita, R; Deur, A; Djalali, C; Doughty, D; Dugger, M; Dupre, R; Egiyan, H; El Alaoui, A; El Fassi, L; Elouadrhiri, L; Fedotov, G; Fegan, S; Forest, T; Garillon, B; Garcon, M; Gevorgyan, N; Ghandilyan, Y; Gilfoyle, G P; Girod, F X; Goetz, J T; Gothe, R W; Griffioen, K A; Guidal, M; Guo, L; Hafidi, K; Hanretty, C; Hattawy, M; Hicks, K; Holtrop, M; Hyde, C E; Ilieva, Y; Ireland, D G; Ishkanov, B I; Isupov, E L; Jiang, H; Jo, H S; Joo, K; Keller, D; Khandaker, M; Kim, A; Kim, W; Klein, F J; Koirala, S; Korover, I; Kuhn, S E; Kubarovsky, V; Lenisa, P; Levine, W I; Livingston, K; Lowry, M; Lu, H Y; MacGregor, I J D; Markov, N; Mayer, M; McKinnon, B; Mineeva, T; Mokeev, V; Movsisyan, A; Munoz Camacho, C; Mustapha, B; Nadel-Turonski, P; Niccolai, S; Niculescu, G; Niculescu, I; Osipenko, M; Pappalardo, L L; Paremuzyan, R; Park, K; Pasyuk, E; Phelps, W; Pisano, S; Pogorelko, O; Price, J W; Procureur, S; Prok, Y; Protopopescu, D; Puckett, A J R; Rimal, D; Ripani, M; Ritchie, B G; Rizzo, A; Rosner, G; Roy, P; Rossi, P; Sabatié, F; Schott, D; Schumacher, R A; Sharabian, Y G; Smith, G D; Shneor, R; Sokhan, D; Stepanyan, S S; Stepanyan, S; Stoler, P; Strauch, S; Sytnik, V; Taiuti, M; Tkachenko, S; Ungaro, M; Vlassov, A V; Voutier, E; Walford, N K; Wei, X; Wood, M H; Wood, S A; Zachariou, N; Zana, L; Zhao, Z W; Zheng, X; Zonta, I
The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using (12)C, (27)Al, (56)Fe, and (208)Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems. Copyright © 2014, American Association for the Advancement of Science.
Correlations in the low-density Fermi gas: Fermi-liquid state, dimerization, and Bardeen-Cooper-Schrieffer pairing
Fan, H. H.; Krotscheck, E.; Lichtenegger, T.; Mateo, D.; Zillich, R. E.
We present ground-state calculations for low-density Fermi gases described by two model interactions, an attractive square-well potential and a Lennard-Jones potential, of varying strength. We use the optimized Fermi-hypernetted chain integral equation method, which has been proved to provide, in the density regimes of interest here, an accuracy of better than 1%. We first examine the low-density expansion of the energy and compare it with the exact answer of H. Huang and C. N. Yang [Phys. Rev. 105, 767 (1957), 10.1103/PhysRev.105.767]. It is shown that a locally correlated wave function of the Jastrow-Feenberg type does not recover the quadratic term in the expansion of the energy in powers of a0kF , where a0 is the vacuum s -wave scattering length and kF the Fermi wave number. The problem is cured by adding second-order perturbation corrections in a correlated basis. Going to higher densities and/or more strongly coupled systems, we encounter an instability of the normal state of the system which is characterized by a divergence of the in-medium scattering length. We interpret this divergence as a phonon-exchange-driven dimerization of the system, similar to what occurs at zero density when the vacuum scattering length a0 diverges. We then study, in the stable regime, the superfluid gap and its dependence on the density and the interaction strength. We identify two corrections to low-density expansions: One is medium corrections to the pairing interaction, and the other is finite-range corrections. We show that the most important finite-range corrections are a direct manifestation of the many-body nature of the system.
PETROLEUM REFINERIES SUPERPHOSPHATE MANUFACTURE CHEMICAL FACTORIES UFg MANUFACTURE SI LICONE AND PLASTICS STEEL MILLS AND METAL FABRICATION...manufacture, enrichment , and reprocessing; gases evolved are, for example, SF-, UFg, HF, organic solvents such as ether, NO , Kr, Xe, I-, Br». c
Advances in atomic spectroscopy
Sneddon, J
This volume continues the series'' cutting-edge reviews on developments in this field. Since its invention in the 1920s, electrostatic precipitation has been extensively used in industrial hygiene to remove dust and particulate matter from gases before entering the atmosphere. This combination of electrostatic precipitation is reported upon in the first chapter. Following this, chapter two reviews recent advances in the area of chemical modification in electrothermal atomization. Chapter three consists of a review which deal with advances and uses of electrothermal atomization atomic absorption spectrometry. Flow injection atomic spectroscopy has developed rapidly in recent years and after a general introduction, various aspects of this technique are looked at in chapter four. Finally, in chapter five the use of various spectrometric techniques for the determination of mercury are described.
Observation of spatial charge and spin correlations in the 2D Fermi-Hubbard model.
Cheuk, Lawrence W; Nichols, Matthew A; Lawrence, Katherine R; Okan, Melih; Zhang, Hao; Khatami, Ehsan; Trivedi, Nandini; Paiva, Thereza; Rigol, Marcos; Zwierlein, Martin W
Strong electron correlations lie at the origin of high-temperature superconductivity. Its essence is believed to be captured by the Fermi-Hubbard model of repulsively interacting fermions on a lattice. Here we report on the site-resolved observation of charge and spin correlations in the two-dimensional (2D) Fermi-Hubbard model realized with ultracold atoms. Antiferromagnetic spin correlations are maximal at half-filling and weaken monotonically upon doping. At large doping, nearest-neighbor correlations between singly charged sites are negative, revealing the formation of a correlation hole, the suppressed probability of finding two fermions near each other. As the doping is reduced, the correlations become positive, signaling strong bunching of doublons and holes, in agreement with numerical calculations. The dynamics of the doublon-hole correlations should play an important role for transport in the Fermi-Hubbard model. Copyright © 2016, American Association for the Advancement of Science.
Adiabatic cooling of a tunable Bose-Fermi mixture in an optical lattice
DEFF Research Database (Denmark)
Sørensen, Ole Søe; Nygaard, Nicolai; Blakie, P.B.
We consider an atomic Fermi gas confined in a uniform optical lattice potential, where the atoms can pair into molecules via a magnetic field controlled narrow Feshbach resonance. Thus by adjusting the magnetic field the portion of fermionic and bosonic particles in the system can be continuously...... varied. We analyze the statistical mechanics of this system and consider the interplay of the lattice physics with the atom-molecule conversion. We study the entropic behavior of the system and characterize the temperature changes that occur during adiabatic ramps across the Feshbach resonance. We show...... that an appropriate choice of filling fraction can be used to reduce the system temperature during such ramps....
Theory of warm ionized gases: equation of state and kinetic Schottky anomaly.
Capolupo, A; Giampaolo, S M; Illuminati, F
Based on accurate Lennard-Jones-type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analog in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed. In particular, the predicted plasma electron density in a sonoluminescent bubble turns out to be in good agreement with the value measured in recent experiments.
Empirical atom model of Vegard's law
Zhang, Lei; Li, Shichun
Vegard's law seldom holds true for most binary continuous solid solutions. When two components form a solid solution, the atom radii of component elements will change to satisfy the continuity requirement of electron density at the interface between component atom A and atom B so that the atom with larger electron density will expand and the atom with the smaller one will contract. If the expansion and contraction of the atomic radii of A and B respectively are equal in magnitude, Vegard's law will hold true. However, the expansion and contraction of two component atoms are not equal in most situations. The magnitude of the variation will depend on the cohesive energy of corresponding element crystals. An empirical atom model of Vegard's law has been proposed to account for signs of deviations according to the electron density at Wigner-Seitz cell from Thomas-Fermi-Dirac-Cheng model.
Fermi Acceleration in driven relativistic billiards
Energy Technology Data Exchange (ETDEWEB)
Pinto, Rafael S., E-mail: firstname.lastname@example.com [Instituto de Fisica ' Gleb Wataghin' , Universidade Estadual de Campinas, 13083-970, Campinas, SP (Brazil); Letelier, Patricio S. [Departamento de Matematica Aplicada, Instituto de Matematica, Estatistica e Computacao Cientifica, Universidade Estadual de Campinas, 13083-859, Campinas, SP (Brazil)
We show numerical experiments of driven billiards using special relativity. We have the remarkable fact that for the relativistic driven circular and annular concentric billiards, depending on initial conditions and parameters, we observe Fermi Acceleration, absent in the Newtonian case. The velocity for these cases tends to the speed of light very quickly. We find that for the annular eccentric billiard the initial velocity grows for a much longer time than the concentric annular billiard until it asymptotically reach c. -- Highlights: → Fermi Acceleration is studied for relativistic driven billiards. → We studied regular and chaotic billiards with different parameters. → Fermi Acceleration is present even for static regular billiards.
Fermi Surface and Antiferromagnetism in Europium Metal
DEFF Research Database (Denmark)
Andersen, O. Krogh; Loucks, T. L.
We have calculated the Fermi surface of europium in order to find those features which determine the wave vector of the helical moment arrangement below the Néel point. We find that there are two pieces of Fermi surface: an electron surface at the symmetry point H, which has the shape of rounded...... of the nearly cubical part of the hole surface at P, and we also discuss the effects of the electron surface at H. Since it is likely that barium and europium have similar Fermi surfaces, we have presented several extremal areas and the corresponding de Haas-van Alphen frequencies in the hope that experimental...
Energy–pressure relation for low-dimensional gases
Directory of Open Access Journals (Sweden)
Francesco Mancarella
Full Text Available A particularly simple relation of proportionality between internal energy and pressure holds for scale-invariant thermodynamic systems (with Hamiltonians homogeneous functions of the coordinates, including classical and quantum – Bose and Fermi – ideal gases. One can quantify the deviation from such a relation by introducing the internal energy shift as the difference between the internal energy of the system and the corresponding value for scale-invariant (including ideal gases. After discussing some general thermodynamic properties associated with the scale-invariance, we provide criteria for which the internal energy shift density of an imperfect (classical or quantum gas is a bounded function of temperature. We then study the internal energy shift and deviations from the energy–pressure proportionality in low-dimensional models of gases interpolating between the ideal Bose and the ideal Fermi gases, focusing on the Lieb–Liniger model in 1d and on the anyonic gas in 2d. In 1d the internal energy shift is determined from the thermodynamic Bethe ansatz integral equations and an explicit relation for it is given at high temperature. Our results show that the internal energy shift is positive, it vanishes in the two limits of zero and infinite coupling (respectively the ideal Bose and the Tonks–Girardeau gas and it has a maximum at a finite, temperature-depending, value of the coupling. Remarkably, at fixed coupling the energy shift density saturates to a finite value for infinite temperature. In 2d we consider systems of Abelian anyons and non-Abelian Chern–Simons particles: as it can be seen also directly from a study of the virial coefficients, in the usually considered hard-core limit the internal energy shift vanishes and the energy is just proportional to the pressure, with the proportionality constant being simply the area of the system. Soft-core boundary conditions at coincident points for the two-body wavefunction introduce
Directory of Open Access Journals (Sweden)
Chaloupecká Hana
Full Text Available Conurbations all over the world have enlarged for numberless years. The accidental or intentional releases of gases become more frequent. Therefore, these crises situations have to be studied. The aim of this paper is to describe experiments examining these processes that were carried out in the laboratory of Environmental Aerodynamics of the Institute of Thermomechanics AS CR in Nový Knín. Results show huge puff variability from replica to replica.
Effect of adding Te to layered GaSe crystals to increase the van der Waals bonding force
Tanabe, Tadao; Zhao, Shu; Sato, Yohei; Oyama, Yutaka
The interplanar binding strength of layered GaSe1-xTex crystals was directly measured using a tensile testing machine. The GaSe1-xTex crystals were grown by a low temperature liquid phase solution method under a controlled Se vapor pressure. The stoichiometry-controlled GaSe1-xTex crystal has the ɛ-polytype structure of GaSe, where the Te atoms are substituted for some of the Se atoms in the GaSe crystal. The effect of adding Te on the bonding strength between the GaSe layers was determined from direct measurements of the van der Waals bonding energy. The bonding energy was increased from 0.023 × 106 N/m2 for GaSe to 0.16 × 106 N/m2 for GaSe1-xTex (x = 0.106).
Advances in atomic, molecular, and optical physics
Berman, Paul R; Arimondo, Ennio
Volume 54 of the Advances Series contains ten contributions, covering a diversity of subject areas in atomic, molecular and optical physics. The article by Regal and Jin reviews the properties of a Fermi degenerate gas of cold potassium atoms in the crossover regime between the Bose-Einstein condensation of molecules and the condensation of fermionic atom pairs. The transition between the two regions can be probed by varying an external magnetic field. Sherson, Julsgaard and Polzik explore the manner in which light and atoms can be entangled, with applications to quantum information processing
The diverse biological properties of the chemically inert noble gases.
Winkler, David A; Thornton, Aaron; Farjot, Géraldine; Katz, Ira
The noble gases represent an intriguing scientific paradox. They are extremely inert chemically but display a remarkable spectrum of clinically useful biological properties. Despite a relative paucity of knowledge of their mechanisms of action, some of the noble gases have been used successfully in the clinic. Studies with xenon have suggested that the noble gases as a class may exhibit valuable biological properties such as anaesthesia; amelioration of ischemic damage; tissue protection prior to transplantation; analgesic properties; and a potentially wide range of other clinically useful effects. Xenon has been shown to be safe in humans, and has useful pharmacokinetic properties such as rapid onset, fast wash out etc. The main limitations in wider use are that: many of the fundamental biochemical studies are still lacking; the lighter noble gases are likely to manifest their properties only under hyperbaric conditions, impractical in surgery; and administration of xenon using convectional gaseous anaesthesia equipment is inefficient, making its use very expensive. There is nonetheless a significant body of published literature on the biochemical, pharmacological, and clinical properties of noble gases but no comprehensive reviews exist that summarize their properties and the existing knowledge of their models of action at the molecular (atomic) level. This review provides such an up-to-date summary of the extensive, useful biological properties of noble gases as drugs and prospects for wider application of these atoms. Crown Copyright © 2016. Published by Elsevier Inc. All rights reserved.
Coupled atomic wires in a synthetic magnetic field
Budich, J. C.; Elben, A.; ŁÄ cki, M.; Sterdyniak, A.; Baranov, M. A.; Zoller, P.
We propose and study systems of coupled atomic wires in a perpendicular synthetic magnetic field as a platform to realize exotic phases of quantum matter. This includes (fractional) quantum Hall states in arrays of many wires inspired by the pioneering work [C. L. Kane et al., Phys. Rev. Lett. 88, 036401 (2002), 10.1103/PhysRevLett.88.036401], as well as Meissner phases and vortex phases in double wires. With one continuous and one discrete spatial dimension, the proposed setup naturally complements recently realized discrete counterparts, i.e., the Harper-Hofstadter model and the two-leg flux ladder, respectively. We present both an in-depth theoretical study and a detailed experimental proposal to make the unique properties of the semicontinuous Harper-Hofstadter model accessible with cold-atom experiments. For the minimal setup of a double wire, we explore how a subwavelength spacing of the wires can be implemented. This construction increases the relevant energy scales by at least an order of magnitude compared to ordinary optical lattices, thus rendering subtle many-body phenomena such as Lifshitz transitions in Fermi gases observable in an experimentally realistic parameter regime. For arrays of many wires, we discuss the emergence of Chern bands with readily tunable flatness of the dispersion and show how fractional quantum Hall states can be stabilized in such systems. Using for the creation of optical potentials Laguerre-Gauss beams that carry orbital angular momentum, we detail how the coupled atomic wire setups can be realized in nonplanar geometries such as cylinders, disks, and tori.
Conoscere Fermi nel centenario della nascita : 29 settembre 1901 - 2001
Bonolis, Luisa
Il lavoro scientifico di Fermi riguarda molti campi disparati, ciascuno dei quali ha avuto uno sviluppo peculiare in tempi successivi alla morte. In questo volume un certo numero di specialisti contemporanei di ciascun settore espone in forma semplice l'idea originaria e la sua successiva evoluzione. INDICE. Carlo Bernardini, "Introduzione"; Giorgio Salvini, "Enrico Fermi. La sua vita, ed un commento alla sua opera"; Edoardo Amaldi, "Commemorazione del Socio Enrico Fermi"; Enrico Persico, "Commemorazione di Enrico Fermi"; Franco Rasetti, "Enrico Fermi e la Fisica Italiana"; Franco Bassani, "Enrico Fermi e la Fisica dello Stato Solido"; Giorgio Parisi, "La statistica di Fermi"; Giovanni Gallavotti, "La meccanica classica e la rivoluzione quantistica nei lavori giovanili di Fermi"; Tullio Levi-Civita, "Sugli invarianti adiabatici"; Bruno Bertotti, "Le coordinate di Fermi e il Principio di Equivalenza"; Marcello Cini, "Fermi e l'elettrodinamica quantistica"; Nicola Cabibbo. "Le interazioni deboli"; Ugo Amaldi, "...
Constraining hadronic models of the Fermi bubbles
Razzaque, Soebur
The origin of sub-TeV gamma rays detected by Fermi-LAT from the Fermi bubbles at the Galactic center is unknown. In a hadronic model, acceleration of protons and/or nuclei and their subsequent interactions with gas in the bubble volume can produce observed gamma ray. Such interactions naturally produce high-energy neutrinos, and detection of those can discriminate between a hadronic and a leptonic origin of gamma rays. Additional constraints on the Fermi bubbles gamma-ray flux in the PeV range from recent HAWC observations restrict hadronic model parameters, which in turn disfavor Fermi bubbles as the origin of a large fraction of neutrino events detected by IceCube along the bubble directions. We revisit our hadronic model and discuss future constraints on parameters from observations in very high-energy gamma rays by CTA and in neutrinos.
Gamma-Ray Astrophysics NSSTC Fermi GBM
National Aeronautics and Space Administration — The Fermi Gamma-Ray Burst Monitor (GBM) is not a pointed or imaging instrument. To determine fluxes for known sources, we measure the change in the count rate...
Fermi Surface of the Most Dilute Superconductor
Directory of Open Access Journals (Sweden)
Xiao Lin
Full Text Available The origin of superconductivity in bulk SrTiO_{3} is a mystery since the nonmonotonous variation of the critical transition with carrier concentration defies the expectations of the crudest version of the BCS theory. Here, employing the Nernst effect, an extremely sensitive probe of tiny bulk Fermi surfaces, we show that, down to concentrations as low as 5.5×10^{17} cm^{-3}, the system has both a sharp Fermi surface and a superconducting ground state. The most dilute superconductor currently known therefore has a metallic normal state with a Fermi energy as little as 1.1 meV on top of a band gap as large as 3 eV. The occurrence of a superconducting instability in an extremely small, single-component, and barely anisotropic Fermi surface implies strong constraints for the identification of the pairing mechanism.
BKGE: Fermi-LAT Background Estimator
Vasileiou, Vlasios
The Fermi-LAT Background Estimator (BKGE) is a publicly available open-source tool that can estimate the expected background of the Fermi-LAT for any observational conguration and duration. It produces results in the form of text files, ROOT files, gtlike source-model files (for LAT maximum likelihood analyses), and PHA I/II FITS files (for RMFit/XSpec spectral fitting analyses). Its core is written in C++ and its user interface in Python.
First Light on GRBs with Fermi
Dermer, Charles D.
Fermi LAT (Large Area Telescope) and GBM (Gamma ray Burst Monitor) observations of GRBs are briefly reviewed, keeping in mind EGRET expectations. Using gamma\\gamma constraints on outflow Lorentz factors, leptonic models are pitted against hadronic models, and found to be energetically favored. Interpretation of the Fermi data on GRBs helps establish whether GRBs accelerate cosmic rays, including those reaching $\\approx 10^{20}$ eV.
Fermi breakup and the statistical multifragmentation model
Energy Technology Data Exchange (ETDEWEB)
Carlson, B.V., E-mail: email@example.com [Departamento de Fisica, Instituto Tecnologico de Aeronautica - CTA, 12228-900 Sao Jose dos Campos (Brazil); Donangelo, R. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cidade Universitaria, CP 68528, 21941-972, Rio de Janeiro (Brazil); Instituto de Fisica, Facultad de Ingenieria, Universidad de la Republica, Julio Herrera y Reissig 565, 11.300 Montevideo (Uruguay); Souza, S.R. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cidade Universitaria, CP 68528, 21941-972, Rio de Janeiro (Brazil); Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, CP 15051, 91501-970, Porto Alegre (Brazil); Lynch, W.G.; Steiner, A.W.; Tsang, M.B. [Joint Institute for Nuclear Astrophysics, National Superconducting Cyclotron Laboratory and the Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
We demonstrate the equivalence of a generalized Fermi breakup model, in which densities of excited states are taken into account, to the microcanonical statistical multifragmentation model used to describe the disintegration of highly excited fragments of nuclear reactions. We argue that such a model better fulfills the hypothesis of statistical equilibrium than the Fermi breakup model generally used to describe statistical disintegration of light mass nuclei.
Sampling and analysis methods for geothermal fluids and gases
Energy Technology Data Exchange (ETDEWEB)
Watson, J.C.
The sampling procedures for geothermal fluids and gases include: sampling hot springs, fumaroles, etc.; sampling condensed brine and entrained gases; sampling steam-lines; low pressure separator systems; high pressure separator systems; two-phase sampling; downhole samplers; and miscellaneous methods. The recommended analytical methods compiled here cover physical properties, dissolved solids, and dissolved and entrained gases. The sequences of methods listed for each parameter are: wet chemical, gravimetric, colorimetric, electrode, atomic absorption, flame emission, x-ray fluorescence, inductively coupled plasma-atomic emission spectroscopy, ion exchange chromatography, spark source mass spectrometry, neutron activation analysis, and emission spectrometry. Material on correction of brine component concentrations for steam loss during flashing is presented. (MHR)
Equilibrium and Non-Equilibrium Condensation Phenomena in Tuneable 3D and 2D Bose Gases
AFRL-AFOSR-UK-TR-2016-0009 Equilibrium and non- equilibrium condensation phenomena in tuneable 3D and 2D Bose gases Zoran Hadzibabic THE CHANCELLOR...31-Aug-2015 4. TITLE AND SUBTITLE Equilibrium and non- equilibrium condensation phenomena in tuneable 3D and 2D Bose gases 5a. CONTRACT NUMBER... equilibrium and non- equilibrium many-body phenomena, trapping ultracold atomic gases in different geometries including both 3 and 2 spatial dimensions
Spectrum of spin waves in cold polarized gases
Energy Technology Data Exchange (ETDEWEB)
Andreeva, T. L., E-mail: firstname.lastname@example.com [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)
The spin dynamics of cold polarized gases are investigated using the Boltzmann equation. The dispersion relation for spin waves (transverse component of the magnetic moment) and the spin diffusion coefficient of the longitudinal component of the magnetic moment are calculated without using fitting parameters. The spin wave frequency and the diffusion coefficient for rubidium atoms are estimated numerically.
Molecular Beam Studies of Reactions Between Stratospheric Gases and Supercooled Sulfuric Acid
National Research Council Canada - National Science Library
Nathanson, Gilbert
Sulfuric acid aerosols in the stratosphere contribute to the destruction of the ozone layer by converting inactive gases like HCl and HBr into molecules that fall apart into chlorine and bromine atoms...
Molecular Beam Studies of Reactions between Stratospheric Gases and Supercooled Sulfuric Acid
National Research Council Canada - National Science Library
Nathanson, Gilbert
Sulfuric acid aerosols in the stratosphere contribute to the destruction of the ozone layer by converting inactive gases like HCl and HBr into molecules that fall apart into chlorine and bromine atoms...
Directory of Open Access Journals (Sweden)
Laurent Chusseau
Full Text Available We show that the thermodynamics of ideal gases may be derived solely from the Democritean concept of corpuscles moving in vacuum plus a principle of simplicity, namely that these laws are independent of the laws of motion, aside from the law of energy conservation. Only a single corpuscle in contact with a heat bath submitted to a z and t-invariant force is considered. Most of the end results are known but the method appears to be novel. The mathematics being elementary, the present paper should facilitate the understanding of the ideal gas law and of classical thermodynamics even though not-usually-taught concepts are being introduced.
Sir William Ramsay and the noble gases.
Davies, Alwyn G
Sir William Ramsay was one of the world's leading scientists at the end of the 19th century, and in a spectacular period of research between 1894 and 1898, he discovered five new elements. These were the noble gases, helium, neon, argon, krypton, and xenon; they added a whole new group to the Periodic Table of the elements, and provided the keystone to our understanding of the electronic structure of atoms, and the way those electrons bind the atoms together into molecules. For this work he was awarded the Nobel Prize in Chemistry in 1904, the first such prize to come to a British subject. He was also a man of great charm, a good linguist, and a composer and performer of music, poetry and song. This review will trace his career, describe his character and give and account of the chemistry which led to the award of the Nobel Prize.
Fermi wave vector for the partially spin-polarized composite-fermion Fermi sea
DEFF Research Database (Denmark)
Coimbatore Balram, Ajit; Jain, Jainendra
The fully spin polarized composite fermion (CF) Fermi sea at half filled lowest Landau level has a Fermi wave vector $k^*_{\\rm F}=\\sqrt{4\\pi\\rho_e}$, where $\\rho_e$ is the density of electrons or composite fermions, supporting the notion that the interaction between composite fermions can...... CFFSs at $\
Nonexistence in Thomas-Fermi-Dirac-von Weizsäcker Theory with Small Nuclear Charges
Energy Technology Data Exchange (ETDEWEB)
Nam, Phan Thành, E-mail: email@example.com [Institute of Science and Technology Austria (Austria); Den Bosch, Hanne Van, E-mail: email@example.com [Pontificia Universidad Católica de Chile, Instituto de Física (Chile)
We study the ionization problem in the Thomas-Fermi-Dirac-von Weizsäcker theory for atoms and molecules. We prove the nonexistence of minimizers for the energy functional when the number of electrons is large and the total nuclear charge is small. This nonexistence result also applies to external potentials decaying faster than the Coulomb potential. In the case of arbitrary nuclear charges, we obtain the nonexistence of stable minimizers and radial minimizers.
Minimum dipole moment required to bind an electron--molecular theorists rediscover phenomenon mentioned in Fermi--Teller paper on another subject twenty years earlier
Energy Technology Data Exchange (ETDEWEB)
Turner, J.E.
Work leading to the discovery of the minimum dipole moment for electron binding, D/sub min/ = 0.639 ea/sub 0/ (atomic units), by several groups in 1967-68 is described. It was subsequently learned that this number had been published in 1947 by Fermi and Teller, who did not, however, indicate how they derived it. The author has found a numerical solution in Fermi's notebooks from 1946-50 at the University of Chicago Library. Fermi's work is described and presented here with relevant material from his notebooks.
Conduction of molecular electronic devices: qualitative insights through atom-atom polarizabilities.
Stuyver, T; Fias, S; De Proft, F; Fowler, P W; Geerlings, P
The atom-atom polarizability and the transmission probability at the Fermi level, as obtained through the source-and-sink-potential method for every possible configuration of contacts simultaneously, are compared for polycyclic aromatic compounds. This comparison leads to the conjecture that a positive atom-atom polarizability is a necessary condition for transmission to take place in alternant hydrocarbons without non-bonding orbitals and that the relative transmission probability for different configurations of the contacts can be predicted by analyzing the corresponding atom-atom polarizability. A theoretical link between the two considered properties is derived, leading to a mathematical explanation for the observed trends for transmission based on the atom-atom polarizability.
Trapped noble gases in meteorites
Swindle, Timothy D.
The trapped noble gases in meteorites come in two main varieties, usually referred to as solar and planetary. The solar noble gases are implanted solar-wind or solar-flare materials, and thus their relative elemental abundances provide a good estimate of those of the sun. The planetary noble gases have relative elemental abundances similar to those in the terrestrial atmosphere, but there are also important distinctions. At least one other elemental pattern (subsolar) and several isotopic patterns have also been identified.
Upgrading Fermi Without Traveling to Space
Kohler, Susanna
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has received an upgrade that increased its sensitivity by a whopping 40% and nobody had to travel to space to make it happen! The difference instead stems from remarkable improvement to the software used to analyze Fermi-LATs data, and it has resulted in a new high-energy map of our sky.Animation (click to watch!) comparing the Pass 7 to the Pass 8 Fermi-LAT analysis, in a region in the constellation Carina. Pass 8 provides more accurate directions for incoming gamma rays, so more of them fall closer to their sources, creating taller spikes and a sharper image. [NASA/DOE/Fermi LAT Collaboration]Pass 8Fermi-LAT has been surveying the whole sky since August 2008. It detects gamma-ray photons by converting them into electron-positron pairs and tracking the paths of these charged particles. But differentiating this signal from the charged cosmic rays that also pass through the detector with a flux that can be 10,000 times larger! is a challenging process. Making this distinction and rebuilding the path of the original gamma ray relies on complex analysis software.Pass 8 is a complete reprocessing of all data collected by Fermi-LAT. The software has gone through many revisions before now, but this is the first revision that has taken into account all of the experience that the Fermi team has gained operating the LAT in its orbital environment.The improvements made in Pass 8 include better background rejection of misclassified charged particles, improvements to the point spread function and effective area of the detector, and an extension of the effective energy range from below 100 MeV to beyond a few hundred GeV. The changes made in Pass 8 have increased the sensitivity of Fermi-LAT by an astonishing 40%.Map of the High-Energy SkySky map of the sources in the 2FHL catalog, classified by their most likely association. Click for a better look! [Ackermann et al. 2016]The first result from the
Observation of Spin-Polarons in a strongly interacting Fermi liquid
Zwierlein, Martin
We have observed spin-polarons in a highly imbalanced mixture of fermionic atoms using tomographic RF spectroscopy. Feshbach resonances allow to freely tune the interactions between the two spin states involved. A single spin down atom immersed in a Fermi sea of spin up atoms can do one of two things: For strong attraction, it can form a molecule with exactly one spin up partner, but for weaker interaction it will spread its attraction and surround itself with a collection of majority atoms. This spin down atom ``dressed'' with a spin up cloud constitutes the spin-polaron. We have observed a striking spectroscopic signature of this quasi-particle for various interaction strengths, a narrow peak in the spin down spectrum that emerges above a broad background. The narrow width signals a long lifetime of the spin-polaron, much longer than the collision rate with spin up atoms, as it must be for a proper quasi-particle. The peak position allows to directly measure the polaron energy. The broad pedestal at high energies reveals physics at short distances and is thus ``molecule-like'': It is exactly matched by the spin up spectra. The comparison with the area under the polaron peak allows to directly obtain the quasi-particle weight Z. We observe a smooth transition from polarons to molecules. At a critical interaction strength of 1/kFa = 0.7, the polaron peak vanishes and spin up and spin down spectra exactly match, signalling the formation of molecules. This is the same critical interaction strength found earlier to separate a normal Fermi mixture from a superfluid molecular Bose-Einstein condensate. The spin-polarons determine the low-temperature phase diagram of imbalanced Fermi mixtures. In principle, polarons can interact with each other and should, at low enough temperatures, form a superfluid of p-wave pairs. We will present a first indication for interactions between polarons.
Fermion pairing in Bose-Fermi mixtures
Matera, F.
An effective interaction between fermions in a Bose-Fermi mixture is derived. It is induced by density fluctuations of the bosonic background. The contributions from states containing both one and two virtual phonons are taken into account self-consistently. The time dependence of the effective interaction has been removed by assuming that the velocity of the fermions at the Fermi surface is much larger than the sound velocity in the Bose gas. This assumption is more appropriate for the actual experimental situations than the usual approximation of neglecting retardation effects. The effective interaction turns out to be attractive and, as a consequence, can give rise to a superconducting phase in the Fermi component of the mixture. The fermions are considered in only one magnetic state, so that pairing can be effective only in odd-l channels. It has been found that the onset of the superconducting phase can occur at temperatures (>100 nK) of the same order of magnitude as the Fermi temperature (˜300 nK), and the energy gap in the excitation spectrum is a small fraction (˜1%) of the Fermi energy.
Static Magnetic Response of Non-Fermi-Liquid Density.
Chen, Jing-Yuan
We consider the response of the density of a fermion ensemble to an applied weak static magnetic field. It is known that, for a noninteracting Fermi gas, this response is fully characterized by the Fermi volume and the Berry curvature on the Fermi surface. Here we show the same result holds for interacting fermions, including a Fermi liquid and a non-Fermi liquid, to all orders in perturbation theory. Our result relies only on the assumption of a well-defined Fermi surface and the general analytic properties of quantum field theory, and is completely model independent.
African Journals Online (AJOL)
controls the electrons around it, and like a strong spring pushes other nuclei away. Later experiments ... 6Cl 2, because its mass number (A) = 12 and its nucleus contains 6 protons and 6 neutrons. However, ... gamma-radiation. Enrico Fermi, the Italian physicist made impor- tant contributions here. It occurred to him to use.
Topology of Fermi surfaces and anomaly inflows
Adem, Alejandro; Camarena, Omar Antolín; Semenoff, Gordon W.; Sheinbaum, Daniel
We derive a rigorous classification of topologically stable Fermi surfaces of non-interacting, discrete translation-invariant systems from electronic band theory, adiabatic evolution and their topological interpretations. For systems on an infinite crystal it is shown that there can only be topologically unstable Fermi surfaces. For systems on a half- space and with a gapped bulk, our derivation naturally yields a K -theory classification. Given the d - 1-dimensional surface Brillouin zone X s of a d-dimensional half-space, our result implies that different classes of globally stable Fermi surfaces belong in K -1 (Xs) for systems with only discrete translation-invariance. This result has a chiral anomaly inflow interpretation, as it reduces to the spectral flow for d = 2. Through equivariant homotopy methods we extend these results for symmetry classes AI, AII, C and D and discuss their corresponding anomaly inflow interpretation.
Topology of Fermi surfaces and anomaly inflows
Energy Technology Data Exchange (ETDEWEB)
Adem, Alejandro; Camarena, Omar Antolín [Department of Mathematics, University of British Columbia,1984 Mathematics Road, Vancouver, V6T 1Z2 (Canada); Semenoff, Gordon W. [Department of Physics and Astronomy, University of British Columbia,6224 Agricultural Road, Vancouver, V6T 1Z1 (Canada); Sheinbaum, Daniel [Department of Mathematics, University of British Columbia,1984 Mathematics Road, Vancouver, V6T 1Z2 (Canada)
We derive a rigorous classification of topologically stable Fermi surfaces of non-interacting, discrete translation-invariant systems from electronic band theory, adiabatic evolution and their topological interpretations. For systems on an infinite crystal it is shown that there can only be topologically unstable Fermi surfaces. For systems on a half-space and with a gapped bulk, our derivation naturally yields a K-theory classification. Given the d−1-dimensional surface Brillouin zone X{sub s} of a d-dimensional half-space, our result implies that different classes of globally stable Fermi surfaces belong in K{sup −1}(X{sub s}) for systems with only discrete translation-invariance. This result has a chiral anomaly inflow interpretation, as it reduces to the spectral flow for d=2. Through equivariant homotopy methods we extend these results for symmetry classes AI, AII, C and D and discuss their corresponding anomaly inflow interpretation.
Fermi-Walker transport and Thomas precession
Pastor Lambare, Justo
An exact derivation of the Thomas precession formula is presented based on the Fermi-Walker transport equation. Given that the Thomas precession effect is not a particularly intuitive phenomenon, such that when discovered in 1925 it took by surprise even experts in relativity theory, Einstein included, an alternative perspective can be useful at an intermediate level for physics students. The existing literature linking the Thomas precession to Fermi-Walker transport use geometric algebra as mathematical tool. Here the mathematics is kept within the limits of the usual vector and tensor algebra commonly used in special relativity theory at a level appropriate for advanced undergraduate and beginning graduate students.
Supernova Remnants with Fermi Large Area Telescope
Directory of Open Access Journals (Sweden)
Caragiulo M.
Full Text Available The Large Area Telescope (LAT, on-board the Fermi satellite, proved to be, after 8 years of data taking, an excellent instrument to detect and observe Supernova Remnants (SNRs in a range of energies running from few hundred MeV up to few hundred GeV. It provides essential information on physical processes that occur at the source, involving both accelerated leptons and hadrons, in order to understand the mechanisms responsible for the primary Cosmic Ray (CR acceleration. We show the latest results in the observation of Galactic SNRs by Fermi-LAT.
A two-dimensional Fermi gas in the BEC-BCS crossover
Energy Technology Data Exchange (ETDEWEB)
Ries, Martin Gerhard
This thesis reports on the preparation of a 2D Fermi gas in the BEC-BCS crossover and the observation of the BKT transition into a quasi long-range ordered superfluid phase. The pair momentum distribution of the gas is probed by means of a matter-wave focusing technique which relies on time-of-flight evolution in a weak harmonic potential. This distribution holds the coherence properties of the gas. The quasi long-range ordered phase manifests itself as a sharp low-momentum peak. The temperature where it forms is identified as the transition temperature. By tuning the temperature and the interaction strength, the phase diagram of the 2D Fermi gas in the BEC-BCS crossover is mapped out. The phase coherence is investigated in a self-interference experiment. Furthermore, algebraic decay of correlations is observed in the trap average of the first order correlation function, which is obtained from the Fourier transform of the pair momentum distribution. This is in qualitative agreement with predictions of homogeneous theory for the superfluid phase in a 2D gas. The presented results provide a foundation for future experimental and theoretical studies of strongly correlated 2D Fermi gases. They might thus help to elucidate complex systems such as the electron gas in high-T{sub c} superconductors.
High order harmonic generation in rare gases
Energy Technology Data Exchange (ETDEWEB)
Budil, Kimberly Susan [Univ. of California, Davis, CA (United States)
The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet (XUV). The process is conceptually simple. A very intense laser pulse (I ~1013-1014 W/cm2) is focused into a dense (~1017 particles/cm3) atomic medium, causing the atoms to become polarized. These atomic dipoles are then coherently driven by the laser field and begin to radiate at odd harmonics of the laser field. This dissertation is a study of both the physical mechanism of harmonic generation as well as its development as a source of coherent XUV radiation. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. In this picture the process is treated in two steps. The atom ionizes via tunneling after which its classical motion in the laser field is studied. Electron trajectories which return to the vicinity of the nucleus may recombine and emit a harmonic photon, while those which do not return will ionize. An experiment was performed to test the validity of this model wherein the trajectory of the electron as it orbits the nucleus or ion core is perturbed by driving the process with elliptically, rather than linearly, polarized laser radiation. The semiclassical theory predicts a rapid turn-off of harmonic production as the ellipticity of the driving field is increased. This decrease in harmonic production is observed experimentally and a simple quantum mechanical theory is used to model the data. The second major focus of this work was on development of the harmonic "source". A series of experiments were performed examining the spatial profiles of the harmonics. The quality of the spatial profile is crucial if the harmonics are to be used as the source for experiments, particularly if they must be refocused.
Thomas-Fermi approximation to pairing in finite Fermi systems. The weak coupling regime
Energy Technology Data Exchange (ETDEWEB)
Vinas, X [Departament d' Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona (Spain); Schuck, P [Institut de Physique Nucleaire, IN2P3-CNRS, Universite Paris-Sud, F-91406 Orsay-Cedex (France); Farine, M, E-mail: firstname.lastname@example.com [Ecole des Mines de Nantes, Universite Nantes, 4, rue Alfred Kastler B.P. 20722 44307 Nantes-Cedex 3 (France)
We present a new semiclassical theory for describing pairing in finite Fermi systems. It is based on taking the h {yields} 0, i.e. Thomas-Fermi, limit of the gap equation written in the basis of the mean field (weak coupling). In addition to the position dependence of the Fermi momentum, the size dependence of the pairing force is also taken into account in this theory. Along isotopic chains the Thomas-Fermi gaps average the well known arch structure shown by the quantal gaps. This structure can be almost recovered in our formalism if some shell fluctuations are included in the level density. We point out that at the drip line nuclear pairing is strongly reduced. This fact is illustrated with the behaviour of the gap in the inner crust of neutron stars.
Fermi and the Art of Estimation
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 1. Fermi and the Art of Estimation. Rajaram Nityananda. General Article Volume 19 Issue 1 January 2014 pp 73-81. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/019/01/0073-0081. Keywords.
Automatic Cloud Bursting under FermiCloud
Energy Technology Data Exchange (ETDEWEB)
Wu, Hao [Fermilab; Shangping, Ren [IIT; Garzoglio, Gabriele [Fermilab; Timm, Steven [Fermilab; Bernabeu, Gerard [Fermilab; Kim, Hyun Woo; Chadwick, Keith; Jang, Haengjin [KISTI, Daejeon; Noh, Seo-Young [KISTI, Daejeon
Cloud computing is changing the infrastructure upon which scientific computing depends from supercomputers and distributed computing clusters to a more elastic cloud-based structure. The service-oriented focus and elasticity of clouds can not only facilitate technology needs of emerging business but also shorten response time and reduce operational costs of traditional scientific applications. Fermi National Accelerator Laboratory (Fermilab) is currently in the process of building its own private cloud, FermiCloud, which allows the existing grid infrastructure to use dynamically provisioned resources on FermiCloud to accommodate increased but dynamic computation demand from scientists in the domains of High Energy Physics (HEP) and other research areas. Cloud infrastructure also allows to increase a private cloud's resource capacity through "bursting" by borrowing or renting resources from other community or commercial clouds when needed. This paper introduces a joint project on building a cloud federation to support HEP applications between Fermi National Accelerator Laboratory and Korea Institution of Science and Technology Information, with technical contributions from the Illinois Institute of Technology. In particular, this paper presents two recent accomplishments of the joint project: (a) cloud bursting automation and (b) load balancer. Automatic cloud bursting allows computer resources to be dynamically reconfigured to meet users' demands. The load balance algorithm which the cloud bursting depends on decides when and where new resources need to be allocated. Our preliminary prototyping and experiments have shown promising success, yet, they also have opened new challenges to be studied
Modelling of Graphene Nanoribbon Fermi Energy
Directory of Open Access Journals (Sweden)
Zaharah Johari
Full Text Available Graphene nanoribbon (GNR is a promising alternative to carbon nanotube (CNT to overcome the chirality challenge as a nanoscale device channel. Due to the one-dimensional behavior of plane GNR, the carrier statistic study is attractive. Research works have been done on carrier statistic study of GNR especially in the parabolic part of the band structure using Boltzmann approximation (nondegenerate regime. Based on the quantum confinement effect, we have improved the fundamental study in degenerate regime for both the parabolic and nonparabolic parts of GNR band energy. Our results demonstrate that the band energy of GNR near to the minimum band energy is parabolic. In this part of the band structure, the Fermi-Dirac integrals are sufficient for the carrier concentration study. The Fermi energy showed the temperature-dependent behavior similar to any other one-dimensional device in nondegenerate regime. However in the degenerate regime, the normalized Fermi energy with respect to the band edge is a function of carrier concentration. The numerical solution of Fermi-Dirac integrals for nonparabolic region, which is away from the minimum energy band structure of GNR, is also presented.
Switchable Fermi surface sheets in greigite
Zhang, B.; de Wijs, G. A.; de Groot, R. A.
Greigite (Fe3S4) and magnetite (Fe3O4) are isostructural and isoelectronic ferrimagnets with quite distinct properties. Electronic structure calculations reveal greigite is a normalmetal in contrast to half-metallic magnetite. Greigite shows a complex Fermi surface with a unique influence of
Angular correlations near the Fermi energy
Fox, D.; Cebra, D.A.; Karn, J.; Parks, C.; Pradhan, A.; Plicht, J. van der; Westfall, G.D.; Wilson, W.K.; Tickle, R.S.
Angular correlations between light particles have been studied to probe the extent to which a thermally equilibrated system is formed in heavy ion collisions near the Fermi energy. Single-light-particle inclusive energy spectra and two-particle large-angle correlations were measured for 40 and 50
Fermi and the Theory of Weak Interactions
Indian Academy of Sciences (India)
IAS Admin
The history of weak interactions starting with. Fermi's creation of the beta decay theory and culminating in its modern avatar in the form of the electroweak gauge theory is described. Dis- coveries of parity violation, matter{antimatter asymmetry, W and Z bosons and neutrino mass are highlighted. Introduction. Sun gives us ...
Enrico Fermi – The Complete Physicist
Indian Academy of Sciences (India)
History of science is replete with towering intellects that have influenced and shaped the direction of development of the field. Of these, some are known for their ...... Jay Orear, Enrico Fermi: The Master Scientist, The Internet – First. University Press, 2004. Address for Correspondence. Amit Roy. Variable Energy Cyclotron.
Fermi and the Theory of Weak Interactions
Rajasekaran, G.
The history of weak interactions starting with Fermi's creation of the beta decay theory and culminating in its modern avatar in the form of the electroweak gauge theory is described. Discoveries of parity violation, matter-antimatter asymmetry, W and Z bosons and neutrino mass are highlighted.
The Chemistry of the Noble Gases, Understanding the Atom Series.
Chernick, Cedric L.
The history of the discovery, isolation, characterization, production and use of argon, krypton, xenon, helium, and radon is followed by an account of early attempts to react them with other elements. The use of the electron shell theory of valence to explain their inertness and the reactions of chemists to the production of xenon compounds is…
Quantum information entropies of ultracold atomic gases in a ...
Indian Academy of Sciences (India)
[2] W W Beckner, Ann. Math. 102, 159 (1975). Bialynicki-Birula and J Mycielski, Commun. Math. Phys. 44, 129 (1975). [3] S R Gadre, S B Sears, S J Chakrovarty and R D Bendale, Phys. Rev. A32, 2602 (1985). [4] V Majernik and T Opatrny, J. Phys. A29, 2187 (1996). [5] R J Yanez, W Van Assche and J S Dehesa, Phys. Rev.
FermiGrid—experience and future plans
Chadwick, K.; Berman, E.; Canal, P.; Hesselroth, T.; Garzoglio, G.; Levshina, T.; Sergeev, V.; Sfiligoi, I.; Sharma, N.; Timm, S.; Yocum, D. R.
Fermilab supports a scientific program that includes experiments and scientists located across the globe. In order to better serve this community, Fermilab has placed its production computer resources in a Campus Grid infrastructure called 'FermiGrid'. The FermiGrid infrastructure allows the large experiments at Fermilab to have priority access to their own resources, enables sharing of these resources in an opportunistic fashion, and movement of work (jobs, data) between the Campus Grid and National Grids such as Open Science Grid (OSG) and the Worldwide LHC Computing Grid Collaboration (WLCG). FermiGrid resources support multiple Virtual Organizations (VOs), including VOs from the OSG, EGEE, and the WLCG. Fermilab also makes leading contributions to the Open Science Grid in the areas of accounting, batch computing, grid security, job management, resource selection, site infrastructure, storage management, and VO services. Through the FermiGrid interfaces, authenticated and authorized VOs and individuals may access our core grid services, the 10,000+ Fermilab resident CPUs, near-petabyte (including CMS) online disk pools and the multi-petabyte Fermilab Mass Storage System. These core grid services include a site wide Globus gatekeeper, VO management services for several VOs, Fermilab site authorization services, grid user mapping services, as well as job accounting and monitoring, resource selection and data movement services. Access to these services is via standard and well-supported grid interfaces. We will report on the user experience of using the FermiGrid campus infrastructure interfaced to a national cyberinfrastructure - the successes and the problems.
FermiGrid - experience and future plans
Energy Technology Data Exchange (ETDEWEB)
Chadwick, K.; Berman, E.; Canal, P.; Hesselroth, T.; Garzoglio, G.; Levshina, T.; Sergeev, V.; Sfiligoi, I.; Timm, S.; Yocum, D.; /Fermilab
Fermilab supports a scientific program that includes experiments and scientists located across the globe. In order to better serve this community, Fermilab has placed its production computer resources in a Campus Grid infrastructure called 'FermiGrid'. The FermiGrid infrastructure allows the large experiments at Fermilab to have priority access to their own resources, enables sharing of these resources in an opportunistic fashion, and movement of work (jobs, data) between the Campus Grid and National Grids such as Open Science Grid and the WLCG. FermiGrid resources support multiple Virtual Organizations (VOs), including VOs from the Open Science Grid (OSG), EGEE and the Worldwide LHC Computing Grid Collaboration (WLCG). Fermilab also makes leading contributions to the Open Science Grid in the areas of accounting, batch computing, grid security, job management, resource selection, site infrastructure, storage management, and VO services. Through the FermiGrid interfaces, authenticated and authorized VOs and individuals may access our core grid services, the 10,000+ Fermilab resident CPUs, near-petabyte (including CMS) online disk pools and the multi-petabyte Fermilab Mass Storage System. These core grid services include a site wide Globus gatekeeper, VO management services for several VOs, Fermilab site authorization services, grid user mapping services, as well as job accounting and monitoring, resource selection and data movement services. Access to these services is via standard and well-supported grid interfaces. We will report on the user experience of using the FermiGrid campus infrastructure interfaced to a national cyberinfrastructure--the successes and the problems.
Monolayer adsorption of noble gases on graphene
Maiga, Sidi M.; Gatica, Silvina M.
We report our results of simulations of the adsorption of noble gases (Kr, Ar, Xe) on graphene. For Kr, we consider two configurations: supported and free-standing graphene, where atoms are adsorbed only on one or two sides of the graphene. For Ar and Xe, we studied only the case of supported graphene. For the single-side adsorption, we calculated the two-dimensional gas-liquid critical temperature for each adsorbate. We determined the different phases of the monolayers and constructed the phase diagrams. We found two-dimensional incommensurate solid phases for krypton, argon and xenon, and a two-dimensional commensurate solid phase for krypton. For double side adsorption of Kr, we do not see evidence of an ordering transition driven by the interlayer forces.
Deep Inelastic Scattering on Ultracold Gases
Hofmann, Johannes; Zwerger, Wilhelm
We discuss Bragg scattering on both Bose and Fermi gases with strong short-range interactions in the deep inelastic regime of large wave vector transfer q , where the dynamic structure factor is dominated by a resonance near the free-particle energy ℏω =ɛq=ℏ2q2/2 m . Using a systematic short-distance expansion, the structure factor at high momentum is shown to exhibit a nontrivial dependence on frequency characterized by two separate scaling regimes. First, for frequencies that differ from the single-particle energy by terms of order O (q ) (i.e., small deviations compared to the single-particle energy), the dynamic structure factor is described by the impulse approximation of Hohenberg and Platzman. Second, deviations of order O (q2) (i.e., of the same order or larger than the single-particle energy) are described by the operator product expansion, with a universal crossover connecting both regimes. The scaling is consistent with the leading asymptotics for a number of sum rules in the large momentum limit. Furthermore, we derive an exact expression for the shift and width of the single-particle peak at large momentum due to interactions, thus extending a result by Beliaev [J. Exp. Theor. Phys. 7, 299 (1958)] for the low-density Bose gas to arbitrary values of the scattering length a . The shift exhibits a maximum around q a ≃1 , which is connected with a maximum in the static structure factor due to strong short-range correlations. For Bose gases with moderate interaction strengths, the theoretically predicted shift is consistent with the value observed by Papp et al. [Phys. Rev. Lett. 101, 135301 (2008), 10.1103/PhysRevLett.101.135301]. Finally, we develop a diagrammatic theory for the dynamic structure factor which accounts for the correlations beyond Bogoliubov theory. It covers the full range of momenta and frequencies and provides an explicit example for the emergence of asymptotic scaling at large momentum.
Foot, Christopher J
This text will thoroughly update the existing literature on atomic physics. Intended to accompany an advanced undergraduate course in atomic physics, the book will lead the students up to the latest advances and the applications to Bose-Einstein Condensation of atoms, matter-wave inter-ferometry and quantum computing with trapped ions. The elementary atomic physics covered in the early chapters should be accessible to undergraduates when they are first introduced to the subject. To complement. the usual quantum mechanical treatment of atomic structure the book strongly emphasizes the experimen
Noble gases in separated meteoritic minerals - Murchison /C2/, Ornans /C3/, Karoonda /C5/, and Abee /E4/
Srinivasan, S.; Gros, J.; Anders, E.
The distribution of all five noble gases was measured in four meteorites of different classes by mass spectrometry and stepwise heating of HCl-HF-insoluble residues and of samples treated with HNO3 and atomic oxygen. The distribution of the gases among the three main phases, chromite, polymer, and the ill-defined Q-phase, was determined, and also the isotopic distribution of the gases in the phases was obtained.
DEFF Research Database (Denmark)
Krüger, Peter; Hofferberth, S.; Haller, E.
Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom-surface distances can be reduced to microns. We discuss experiments in this regime...
High energy neutrinos from the Fermi bubbles.
Lunardini, Cecilia; Razzaque, Soebur
Recently the Fermi-LAT data have revealed two gamma-ray emitting bubble-shaped structures at the Galactic center. If the observed gamma rays have hadronic origin (collisions of accelerated protons), the bubbles must emit high energy neutrinos as well. This new, Galactic, neutrino flux should trace the gamma-ray emission in spectrum and spatial extent. Its highest energy part, above 20-50 TeV, is observable at a kilometer-scale detector in the northern hemisphere, such as the planned KM3NeT, while interesting constraints on it could be obtained by the IceCube Neutrino Observatory at the South Pole. The detection or exclusion of neutrinos from the Fermi bubbles will discriminate between hadronic and leptonic models, thus bringing unique information on the still mysterious origin of these objects and on the time scale of their formation.
A Probabilistic Analysis of the Fermi Paradox
Solomonides, Evan; Terzian, Yervant
The fermi paradox uses an appeal to the mediocrity principle to make it seem counter-intuitive that humanity has not been contacted by extraterrestrial intelligence. A numerical, statistical analysis was conducted to determine whether this apparent loneliness is, in fact, unexpected. An inequality was derived to relate the frequency of life arising and developing technology on a suitable planet in the galaxy, the average length of time since the first broadcast of such a civilization, and a constant term. An analysis of the sphere reached thus far by human communication was also conducted, considering our local neighborhood and planets of particular interest. We clearly show that human communication has not reached a number of stars and planets adequate to expect an answer. These analyses both conclude that the Fermi paradox is not, in fact, unexpected. By the mediocrity principle and numerical modeling, it is actually unlikely that the Earth would have been reached by extraterrestrial communication at this p...
Scattering resonances in a degenerate Fermi gas
DEFF Research Database (Denmark)
Challis, Katharine; Nygaard, Nicolai; Mølmer, Klaus
We consider elastic single-particle scattering from a one-dimensional trapped two-component superfluid Fermi gas when the incoming projectile particle is identical to one of the confined species. Our theoretical treatment is based on the Hartree-Fock ground state of the trapped gas and a configur......We consider elastic single-particle scattering from a one-dimensional trapped two-component superfluid Fermi gas when the incoming projectile particle is identical to one of the confined species. Our theoretical treatment is based on the Hartree-Fock ground state of the trapped gas...... and a configuration-interaction description of the excitations. We determine the scattering phase shifts for the system and predict Fano-type scattering resonances that are a direct consequence of interatomic pairing. We describe the main characteristics of the scattering resonances and make a comparison...
Unconventional Fermi surface in an insulating state
Energy Technology Data Exchange (ETDEWEB)
Harrison, Neil [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tan, B. S. [Cambridge Univ., Cambridge (United Kingdom); Hsu, Y. -T. [Cambridge Univ., Cambridge (United Kingdom); Zeng, B. [National High Magnetic Field Lab., Tallahassee, FL (United States); Hatnean, M. Ciomaga [Univ. of Warwick, Coventry (United Kingdom); Zhu, Z. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hartstein, M. [Cambridge Univ., Cambridge (United Kingdom); Kiourlappou, M. [Cambridge Univ., Cambridge (United Kingdom); Srivastava, A. [Cambridge Univ., Cambridge (United Kingdom); Johannes, M. D. [Center for Computational Materials Science, Washington, DC (United States); Murphy, T. P. [National High Magnetic Field Lab., Tallahassee, FL (United States); Park, J. -H. [National High Magnetic Field Lab., Tallahassee, FL (United States); Balicas, L. [National High Magnetic Field Lab., Tallahassee, FL (United States); Lonzarich, G. G. [Cambridge Univ., Cambridge (United Kingdom); Balakrishnan, G. [Univ. of Warwick, Coventry (United Kingdom); Sebastian, Suchitra E. [Cambridge Univ., Cambridge (United Kingdom)
Insulators occur in more than one guise; a recent finding was a class of topological insulators, which host a conducting surface juxtaposed with an insulating bulk. Here, we report the observation of an unusual insulating state with an electrically insulating bulk that simultaneously yields bulk quantum oscillations with characteristics of an unconventional Fermi liquid. We present quantum oscillation measurements of magnetic torque in high-purity single crystals of the Kondo insulator SmB6, which reveal quantum oscillation frequencies characteristic of a large three-dimensional conduction electron Fermi surface similar to the metallic rare earth hexaborides such as PrB6 and LaB6. As a result, the quantum oscillation amplitude strongly increases at low temperatures, appearing strikingly at variance with conventional metallic behavior.
Energy Technology Data Exchange (ETDEWEB)
Pittel, S. [Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, 19716 Delaware (United States); Dussel, G. G. [Departamento de Fisica J.J. Giambiagi, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Dukelsky, J.; Sarriguren, P. [Instituto de Estructura de la Materia, CSIC, Serrano 123, 28006 Madrid (Spain)
We describe recent efforts to study Cooper pairs in atomic nuclei. We consider a self-consistent Hartree Fock mean field for the even Sm isotopes and compare results based on three treatments of pairing correlations: a BCS treatment, a number-projected BCS treatment and an exact treatment using the Richardson Ansatz. Significant differences are seen in the pairing correlation energies. Furthermore, because it does not average over the properties of the fermion pairs, the Richardson solution permits a more meaningful definition of the Cooper wave function and of the fraction of pairs that are collective. Our results confirm that only a few pairs near the Fermi surface in realistic atomic nuclei are collective. (Author)
A Probabilistic Analysis of the Fermi Paradox
Solomonides, Evan; Terzian, Yervant
The fermi paradox uses an appeal to the mediocrity principle to make it seem counter-intuitive that humanity has not been contacted by extraterrestrial intelligence. A numerical, statistical analysis was conducted to determine whether this apparent loneliness is, in fact, unexpected. An inequality was derived to relate the frequency of life arising and developing technology on a suitable planet in the galaxy, the average length of time since the first broadcast of such a civilization, and a c...
Fermi/GBM Results of Magnetars
Kouveliotou, chryssa
Magnetars are magnetically powered rotating neutron stars with extreme magnetic fields (over 10(exp 14) Gauss). They were discovered in the X- and gamma-rays where they predominantly emit their radiation. Very few sources (roughly 18) have been found since their discovery in 1987. NASA's Fermi Gamma-ray Space Telescope was launched June 11,2009; since then the Fermi Gamma-ray Burst Monitor (GBM) recorded emission from four magnetar sources. Two of these were brand new sources, SGR J0501 +4516, discovered with Swift and extensively monitored with Swift and GBM, SGR J0418+5729, discovered with GBM and the Interplanetary Network (IPN). A third was SGR Jl550-5418, a source originally classified as an Anomalous X-ray Pulsar (AXP IEI547.0-5408), but exhibiting a very prolific outburst with over 400 events recorded in January 2009. In my talk I will give a short history of magnetars and describe how this, once relatively esoteric field, has emerged as a link between several astrophysical areas including Gamma-Ray Bursts. Finally, I will describe the exciting new results of Fermi in this field and the current status of our knowledge of the magnetar population properties and magnetic fields.
Fermi Results on Gamma-Ray Pulsars
Razzano, Massimiliano; Guillemot, Lucas
By detecting pulsed gamma-ray emission from more than 130 young and recycled pulsars since it began operating in 2008, the Large Area Telescope (LAT) on the Fermi satellite has revolutionized our view of the gamma-ray pulsar population. In addition to detecting and characterizing the gamma-ray emission from many more pulsars, the LAT has discovered a large number of new gamma-ray sources whose properties suggest that they harbor unknown gamma-ray pulsars. Radio observations in support of the Fermi mission have provided a vital contribution to the success of LAT pulsar studies. For instance, radio detections or non-detections of LAT-discovered pulsars constrain the ratio of radio-loud to radio-quiet pulsars, and radio searches in LAT unassociated sources have uncovered several tens of new millisecond pulsars. In this presentation I will summarize some of the main results and implications from pulsar observations with the Fermi LAT and supporting multi-wavelength observations, in particular in the radio domain.
Observation of relativistic antihydrogen atoms
Energy Technology Data Exchange (ETDEWEB)
Blanford, Glenn DelFosse
An observation of relativistic antihydrogen atoms is reported in this dissertation. Experiment 862 at Fermi National Accelerator Laboratory observed antihydrogen atoms produced by the interaction of a circulating beam of high momentum (3 < p < 9 GeV/c) antiprotons and a jet of molecular hydrogen gas. Since the neutral antihydrogen does not bend in the antiproton source magnets, the detectors could be located far from the interaction point on a beamline tangent to the storage ring. The detection of the antihydrogen is accomplished by ionizing the atoms far from the interaction point. The positron is deflected by a magnetic spectrometer and detected, as are the back to back photons resulting from its annihilation. The antiproton travels a distance long enough for its momentum and time of flight to be measured accurately. A statistically significant sample of 101 antihydrogen atoms has been observed. A measurement of the cross section for {bar H}{sup 0} production is outlined within. The cross section corresponds to the process where a high momentum antiproton causes e{sup +} e{sup -} pair creation near a nucleus with the e{sup +} being captured by the antiproton. Antihydrogen is the first atom made exclusively of antimatter to be detected. The observation experiment's results are the first step towards an antihydrogen spectroscopy experiment which would measure the n = 2 Lamb shift and fine structure.
Simultaneous current-, force- and work function measurement with atomic resolution
Herz, Markus; Schiller, Christian H.; Giessibl, Franz J.; Mannhart, Jochen
The local work function of a surface determines the spatial decay of the charge density at the Fermi level normal to the surface. Here, we present a method that enables simultaneous measurements of local work function and tip-sample forces. A combined dynamic scanning tunneling microscope and atomic force microscope is used to measure the tunneling current between an oscillating tip and the sample in real time as a function of the cantilever's deflection. Atomically resolved work function mea...
Wigner's phase-space function and atomic structure: II. Ground states for closed-shell atoms
DEFF Research Database (Denmark)
Springborg, Michael; Dahl, Jens Peder
display and analyze the function for the closed-shell atoms helium, beryllium, neon, argon, and zinc in the Hartree-Fock approximation. The quantum-mechanical exact results are compared with those obtained with the approximate Thomas-Fermi description of electron densities in phase space....
Desulphurization of exhaust gases in chemical processes
Energy Technology Data Exchange (ETDEWEB)
Asperger, K.; Wischnewski, W.
The sulfur content of exhaust gases can be reduced by: desulphurization of fuels; modification of processes; or treatment of resultant gases. In this paper a few selected examples from the chemical industry in the German Democratic Republic are presented. Using modified processes and treating the resultant gases, the sulphuric content of exhaust gases is effectively reduced. Methods to reduce the sulfur content of exhaust gases are described in the field of production of: sulphuric acid; viscose; fertilizers; and paraffin.
Charge transfer effects on the Fermi surface of Ba0.5K 0.5Fe2As2
Nazir, Safdar
Ab-initio calculations within density functional theory are performed to obtain a more systematic understanding of the electronic structure of iron pnictides. As a prototypical compound we study Ba0.5K 0.5Fe2As2 and analyze the changes of its electronic structure when the interaction between the Fe2As 2 layers and their surrounding is modified. We find strong effects on the density of states near the Fermi energy as well as the Fermi surface. The role of the electron donor atoms in iron pnictides thus cannot be understood in a rigid band picture. Instead, the bonding within the Fe2As 2 layers reacts to a modified charge transfer from the donor atoms by adapting the intra-layer Fe-As hybridization and charge transfer in order to maintain an As3- valence state. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
A calculation of internal kinetic energy and polarizability of compressed argon from the statistical atom model
Seldam, C.A. ten; Groot, S.R. de
From Jensen's and Gombás' modification of the statistical Thomas-Fermi atom model, a theory for compressed atoms is developed by changing the boundary conditions. Internal kinetic energy and polarizability of argon are calculated as functions of pressure. At 1000 atm. an internal kinetic energy of
[CFC gases in medicinal sprays].
Pedersen, P H; Svendsen, U G
In 1987, approximately 1.18 million aerosol dispensers for medicinal use were sold in Denmark. These contained approximately 29 tons of completely halogenized CFC gases ("Freon") and the preparations were employed for the treatment of bronchial asthma and rhinitis. The possibilities of substitutes are discussed in this article. Preparations are already available which do not contain CFC. Producers of CFC are also attempting to develop new aerosol gases which do not damage the environment. Perhaps these will be found in medicinal preparations in the future.
Merging of single-particle levels in finite Fermi systems
Khodel, V. A.; Clark, J. W.; Li, Haochen; Zverev, M. V.
Properties of the distribution of single-particle levels adjacent to the Fermi surface in finite Fermi systems are studied, focusing on the case in which these levels are degenerate. The interaction of the quasiparticles occupying these levels lifts the degeneracy and affects the distance between the closest levels on opposite sides of the Fermi surface, as the number of particles in the system is varied. In addition to the familiar scenario of level crossing, a new phenomenon is uncovered, i...
Fermi Large Area Telescope Observations of the Dark Accelerator HESS J1745-303
Directory of Open Access Journals (Sweden)
Paul Yeung
Full Text Available Reviewing the two MeV-GeV investigations in the field of the HESS J1745-303 performed using Fermi Large Area Telescope data, we confirmed that the emission peak comfortably coincides with 'Region A' in the TeV regime, which is the brightest part of this feature. The MeV–TeV spectrum can be precisely described by a single power-law. Also, recent investigation has shown that the MeV-GeV feature is elongated from 'Region A' toward the north-west, which is similar to the case of largescale atomic/molecular gas distribution.
Extended Thomas-Fermi density functionals in the presence of a tensor interaction in spherical symmetry
Bartel, J.; Bencheikh, K.; Meyer, J.
For a one-body Hamiltonian obtained from the energy-density functional associated with a Skyrme effective interaction, including a tensor force, semiclassical functional densities are derived in the framework of the Extended Thomas-Fermi method, in spherical symmetry, for the kinetic energy and spin-orbit density. The structure of the self-consistent mean-field potentials constructed with such semiclassical functionals is studied. The impact of the tensor force in particular on the spin-orbit form factor clearly indicates the necessity of including such tensor-force terms in the theoretical description of atomic nuclei and their possible influence on the shell structure of exotic nuclei.
Indian Academy of Sciences (India)
http://www.ias.ac.in/article/fulltext/reso/015/10/0905-0925. Keywords. Atomic theory; Avogadro's hypothesis; atomic weights; periodic table; valence; molecular weights; molecular formula; isomerism. Author Affiliations. S Ramasesha1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, ...
A Nonlocal Poisson-Fermi Model for Ionic Solvent
Xie, Dexuan; Eisenberg, Bob; Scott, L Ridgway
We propose a nonlocal Poisson-Fermi model for ionic solvent that includes ion size effects and polarization correlations among water molecules in the calculation of electrostatic potential. It includes the previous Poisson-Fermi models as special cases, and its solution is the convolution of a solution of the corresponding nonlocal Poisson dielectric model with a Yukawa-type kernel function. Moreover, the Fermi distribution is shown to be a set of optimal ionic concentration functions in the sense of minimizing an electrostatic potential free energy. Finally, numerical results are reported to show the difference between a Poisson-Fermi solution and a corresponding Poisson solution.
Fermi resonance in CO2: Mode assignment and quantum nuclear effects from first principles molecular dynamics
Basire, Marie; Mouhat, Félix; Fraux, Guillaume; Bordage, Amélie; Hazemann, Jean-Louis; Louvel, Marion; Spezia, Riccardo; Bonella, Sara; Vuilleumier, Rodolphe
Vibrational spectroscopy is a fundamental tool to investigate local atomic arrangements and the effect of the environment, provided that the spectral features can be correctly assigned. This can be challenging in experiments and simulations when double peaks are present because they can have different origins. Fermi dyads are a common class of such doublets, stemming from the resonance of the fundamental excitation of a mode with the overtone of another. We present a new, efficient approach to unambiguously characterize Fermi resonances in density functional theory (DFT) based simulations of condensed phase systems. With it, the spectral features can be assigned and the two resonating modes identified. We also show how data from DFT simulations employing classical nuclear dynamics can be post-processed and combined with a perturbative quantum treatment at a finite temperature to include analytically thermal quantum nuclear effects. The inclusion of these effects is crucial to correct some of the qualitative failures of the Newtonian dynamics simulations at a low temperature such as, in particular, the behavior of the frequency splitting of the Fermi dyad. We show, by comparing with experimental data for the paradigmatic case of supercritical CO2, that these thermal quantum effects can be substantial even at ambient conditions and that our scheme provides an accurate and computationally convenient approach to account for them.
Detection of gas atoms with carbon nanotubes
Arash, B.; Wang, Q.
Owning to their unparalleled sensitivity resolution, nanomechanical resonators have excellent capabilities in design of nano-sensors for gas detection. The current challenge is to develop new designs of the resonators for differentiating distinct gas atoms with a recognizably high sensitivity. In this work, the characteristics of impulse wave propagation in carbon nanotube-based sensors are investigated using molecular dynamics simulations to provide a new method for detection of noble gases. A sensitivity index based on wave velocity shifts in a single-walled carbon nanotube, induced by surrounding gas atoms, is defined to explore the efficiency of the nano-sensor. The simulation results indicate that the nano-sensor is able to differentiate distinct noble gases at the same environmental temperature and pressure. The inertia and the strengthening effects by the gases on wave characteristics of carbon nanotubes are particularly discussed, and a continuum mechanics shell model is developed to interpret the effects.
Hilton, D. R.; Porcelli, D.
The study of the noble gases has been associated with some of the most illustrious names in experimental science, and some of the most profound discoveries. Fundamental advances in nuclear chemistry and physics - including the discovery of isotopes - have resulted from their study, earning Nobel Prizes for a number of early practitioners (Rutherford in 1908; Soddy in 1921; Aston in 1922) as well as for their discoverers (Ramsay and Rayleigh in 1904). Within the Earth Sciences, the noble gases found application soon after discovery - helium was used as a chronometer to estimate formation ages of various minerals (Strutt, 1908). In more recent times, the emphasis of noble gas research has shifted to include their exploitation as inert tracers of geochemical processes. In large part, this shift stems from the realization that primordial volatiles have been stored within the Earth since the time of planetary accretion and are still leaking to the surface today. In this introduction, we give a brief overview of the discovery of the noble gases and their continuing utility in the Earth Sciences, prior to setting into perspective the present contribution, which focuses on noble gases in the Earth's mantle.
DEFF Research Database (Denmark)
Antipin, Oleg; Sannino, Francesco; Tuominen, Kimmo
The discovery of a light Higgs boson at LHC may be suggesting that we need to revise our model building paradigms to understand the origin of the weak scale. We explore the possibility that the Fermi scale is not fundamental but rather a derived one, i.e. a low energy mirage. We show that this sc......\\sim 10^{10}$ GeV and the other around $M_{\\rm U} \\sim 10^{16}$ GeV, although other values are also possible....
Path-integral calculation of the third virial coefficient of quantum gases at low temperatures.
Garberoglio, Giovanni; Harvey, Allan H
We derive path-integral expressions for the second and third virial coefficients of monatomic quantum gases. Unlike previous work that considered only Boltzmann statistics, we include exchange effects (Bose-Einstein or Fermi-Dirac statistics). We use state-of-the-art pair and three-body potentials to calculate the third virial coefficient of (3)He and (4)He in the temperature range 2.6-24.5561 K. We obtain uncertainties smaller than those of the limited experimental data. Inclusion of exchange effects is necessary to obtain accurate results below about 7 K.
Turbomolecular Pumps for Holding Gases in Open Containers
Keller, John W.; Lorenz, John E.
Proposed special-purpose turbomolecular pumps denoted turbotraps would be designed, along with mating open containers, to prevent the escape of relatively slowly (thermal) moving gas molecules from the containers while allowing atoms moving at much greater speeds to pass through. In the original intended applications, the containers would be electron-attachment cells, and the contained gases would be vapors of alkali metal atoms moving at thermal speeds that would be of the order of a fraction of 300 meters per second. These cells would be parts of apparatuses used to measure fluxes of neutral atoms incident at kinetic energies in the approximate range of 10 eV to 10 keV (corresponding to typical speeds of the order of 40,000 m/s and higher). The incident energetic neutral atoms would pass through the cells, wherein charge-exchange reactions with the alkali metal atoms would convert the neutral atoms to negative ions, which, in turn, could then be analyzed by use of conventional charged-particle optics.
Fermi LAT Observations of LS 5039
Energy Technology Data Exchange (ETDEWEB)
Abdo, A.A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Blandford, R.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique /Washington U., Seattle /Padua U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /Milan Polytechnic /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /NASA, Goddard /NASA, Goddard /CSST, Baltimore /DAPNIA, Saclay /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Sonoma State U. /Stockholm U. /Stockholm U., OKC /DAPNIA, Saclay /NASA, Goddard /CSST, Baltimore /SLAC /ASDC, Frascati /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC /Grenoble Observ. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U.; /more authors..
The first results from observations of the high-mass X-ray binary LS 5039 using the Fermi Gamma-ray Space Telescope data between 2008 August and 2009 June are presented. Our results indicate variability that is consistent with the binary period, with the emission being modulated with a period of 3.903 {+-} 0.005 days; the first detection of this modulation at GeV energies. The light curve is characterized by a broad peak around superior conjunction in agreement with inverse Compton scattering models. The spectrum is represented by a power law with an exponential cutoff, yielding an overall flux (100 MeV-300 GeV) of 4.9 {+-} 0.5(stat) {+-} 1.8(syst) x 10{sup -7} photon cm{sup -2} s{sup -1}, with a cutoff at 2.1 {+-} 0.3(stat) {+-} 1.1(syst) GeV and photon index {Gamma} = 1.9 {+-} 0.1(stat) {+-} 0.3(syst). The spectrum is observed to vary with orbital phase, specifically between inferior and superior conjunction. We suggest that the presence of a cutoff in the spectrum may be indicative of magnetospheric emission similar to the emission seen in many pulsars by Fermi.
Fermi Liquid Instabilities in the Spin Channel
Energy Technology Data Exchange (ETDEWEB)
Wu, Congjun; /Santa Barbara, KITP; Sun, Kai; Fradkin, Eduardo; /Illinois U., Urbana; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
We study the Fermi surface instabilities of the Pomeranchuk type in the spin triplet channel with high orbital partial waves (F{sub l}{sup a} (l > 0)). The ordered phases are classified into two classes, dubbed the {alpha} and {beta}-phases by analogy to the superfluid {sup 3}He-A and B-phases. The Fermi surfaces in the {alpha}-phases exhibit spontaneous anisotropic distortions, while those in the {beta}-phases remain circular or spherical with topologically non-trivial spin configurations in momentum space. In the {alpha}-phase, the Goldstone modes in the density channel exhibit anisotropic overdamping. The Goldstone modes in the spin channel have nearly isotropic underdamped dispersion relation at small propagating wavevectors. Due to the coupling to the Goldstone modes, the spin wave spectrum develops resonance peaks in both the {alpha} and {beta}-phases, which can be detected in inelastic neutron scattering experiments. In the p-wave channel {beta}-phase, a chiral ground state inhomogeneity is spontaneously generated due to a Lifshitz-like instability in the originally nonchiral systems. Possible experiments to detect these phases are discussed.
Fermi's paradox: The last challenge for copernicanism?
Directory of Open Access Journals (Sweden)
Ćirković M.M.
Full Text Available We review Fermi's paradox (or the 'Great Silence' problem, not only arguably the oldest and crucial problem for the Search for ExtraTerrestrial Intelligence (SETI, but also a conundrum of profound scientific, philosophical and cultural importance. By a simple analysis of observation selection effects, the correct resolution of Fermi's paradox is certain to tell us something about the future of humanity. Already more than three quarters of century old puzzle and a quarter of century since the last major review paper in the field by G. David Brin has generated many ingenious discussions and hypotheses. We analyze the often tacit methodological assumptions built in various answers to this puzzle and attempt a new classification of the numerous solutions proposed in an already huge literature on the subject. Finally, we consider the ramifications of various classes of hypotheses for the practical SETI projects. Somewhat paradoxically, it seems that the class of (neocatastrophic hypotheses gives, on the balance, the strongest justification to optimism regarding our current and near-future SETI efforts.
Fermi's Paradox - The Last Challenge For Copernicanism?
Directory of Open Access Journals (Sweden)
Ćirković, M. M.
Full Text Available We review Fermi's paradox (or the "Great Silence" problem, not only arguably the oldest and crucial problem for the Search for ExtraTerrestrial Intelligence (SETI, but also a conundrum of profound scientific, philosophical and cultural importance. By a simple analysis of observation selection effects, the correct resolution of Fermi's paradox is certain to tell us something about the future of humanity. Already more than three quarters of century old puzzle -- and a quarter of century since the last major review paper in the field by G. David Brin -- has generated many ingenious discussions and hypotheses. We analyze the often tacit methodological assumptions built in various answers to this puzzle and attempt a new classification of the numerous solutions proposed in an already huge literatureon the subject. Finally, we consider the ramifications of variousclasses of hypotheses for the practical SETI projects. Somewhatparadoxically, it seems that the class of (neocatastrophichypotheses gives, on the balance, the strongest justification tooptimism regarding our current and near-future SETI efforts.
The First Fermi LAT Supernova Remnant Catalog
Acero, F.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caputo, R.; Caragiulo, M.; Caraveo, P. A.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cohen, J. M.; Cohen-Tanugi, J.; Cominsky, L. R.; Condon, B.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Digel, S. W.; Di Venere, L.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Ferrara, E. C.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Grondin, M.-H.; Guillemot, L.; Guiriec, S.; Gustafsson, M.; Hadasch, D.; Harding, A. K.; Hayashida, M.; Hays, E.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Hou, X.; Iafrate, G.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, J.; Katsuta, J.; Kerr, M.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Laffon, H.; Lande, J.; Larsson, S.; Latronico, L.; Lemoine-Goumard, M.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill, J.; Maldera, S.; Marelli, M.; Mayer, M.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nemmen, R.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Perkins, J. S.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Renaud, M.; Reposeur, T.; Rousseau, R.; Saz Parkinson, P. M.; Schmid, J.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Strong, A. W.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tibolla, O.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Vianello, G.; Wells, B.; Wood, K. S.; Wood, M.; Yassine, M.; den Hartog, P. R.; Zimmer, S.
To uniformly determine the properties of supernova remnants (SNRs) at high energies, we have developed the first systematic survey at energies from 1 to 100 GeV using data from the Fermi Large Area Telescope (LAT). Based on the spatial overlap of sources detected at GeV energies with SNRs known from radio surveys, we classify 30 sources as likely GeV SNRs. We also report 14 marginal associations and 245 flux upper limits. A mock catalog in which the positions of known remnants are scrambled in Galactic longitude allows us to determine an upper limit of 22% on the number of GeV candidates falsely identified as SNRs. We have also developed a method to estimate spectral and spatial systematic errors arising from the diffuse interstellar emission model, a key component of all Galactic Fermi LAT analyses. By studying remnants uniformly in aggregate, we measure the GeV properties common to these objects and provide a crucial context for the detailed modeling of individual SNRs. Combining our GeV results with multiwavelength (MW) data, including radio, X-ray, and TeV, we demonstrate the need for improvements to previously sufficient, simple models describing the GeV and radio emission from these objects. We model the GeV and MW emission from SNRs in aggregate to constrain their maximal contribution to observed Galactic cosmic rays.
Induced interactions in a superfluid Bose-Fermi mixture
DEFF Research Database (Denmark)
Kinnunen, Jami; Bruun, Georg
We analyze a Bose-Einstein condensate (BEC) mixed with a superfluid two-component Fermi gas in the whole BCS-BEC crossover. Using a quasiparticle random-phase approximation combined with Beliaev theory to describe the Fermi superfluid and the BEC, respectively, we show that the single...
Time domain astronomy with Swift and Fermi | Gehrels | Rwanda ...
African Journals Online (AJOL)
Swift and Fermi are unveiling an unexpectedly rich tapestry of behavior in the transient γ−ray sky. Sources which were already known to be transient − such as pulsars, gamma-ray bursts, and blazars − have been studied in ever-increasing detail. For example, Fermi/LAT has detected 117 pulsars of which 56 are new.
Control of pollutants in flue gases and fuel gases
Energy Technology Data Exchange (ETDEWEB)
Zevenhoven, R. [Helsinki Univ. of Technology, Otaniemi (Finland); Kilpinen, P. [Aabo Akademi Univ., Turku (Finland)
Funding from the Nordic Energy Research Programme and from Helsinki University of Technology allowed for the preparation of this e-book, accompanied by overhead sheets as presented during the lectures. All material can be downloaded as pdf documents from the internet-address http://www.hut.fi/-rzeveho//gasbook, hence the qualification e- book Updates will be produced chapter-by-chapter in the future. Objectives and scope. Textbooks on this subject are, in general, limited to what can be called 'conventional' flue gas cleaning for conventional pulverised coal combustion processes, i.e. wet flue gas desulphurisation (FGD), bag filters and electrostatic precipitators for flyash and selective catalytic reduction (SCR) for NO{sub x} control. Other books address waste incineration within a discussion on waste management. The scope of this material we tried to make more up-to-date and therefore wider than these texts. Apart from pollutant control the formation of the pollutants is briefly addressed, which often provides the key to abatement methods as an alternative to control methods. Secondly, more species are addressed such HS in addition to SO{sub 2}; N{sub 2}0, HCN and NH{sub 3} in addition to NO{sub x}; alkali metals and trace elements such as mercury, halogenic compounds such as HO and dioxines and furanes; and volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs). Also greenhouse gases, mainly CO{sub 2}, and ozone-depleting gases, such as CFCs, are briefly discussed. The motivation for this was to cover flue gases from combustion as well as fuel gases from gasification processes, using various types of furnaces and boilers, and to extend the range of chemical compounds to those found in the product gases in waste incineration and energy-from-waste processes. Finally, not only 'cold' gas cleaning but also 'hot' gas cleaning is addressed. All this in an attempt to cover the wide spectrum of pollutants found in
Control of pollutants in flue gases and fuel gases
Energy Technology Data Exchange (ETDEWEB)
Zevenhoven, R.; Kilpinen, P.
Textbooks on this subject are, in general, limited to what can be called 'conventional' flue gas cleaning for conventional pulverised coal combustion processes, i.e. wet flue gas desulphurisation (FGD), bag filters and electrostatic precipitators for flyash and selective catalytic reduction (SCR) for NO{sub x} control. Other books address waste incineration within a discussion on waste management. The scope of this material we tried to make more up-to-date and therefore wider than these texts. Apart from pollutant control the formation of the pollutants is briefly addressed, which often provides the key to abatement methods as an alternative to control methods. Secondly, more species are addressed such HS in addition to SO{sub 2}; N{sub 2}O, HCN and NH{sub 3} in addition to NO{sub x}; alkali metals and trace elements such as mercury, halogenic compounds such as HO and dioxines and furanes; and volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs). Also greenhouse gases, mainly CO{sub 2}, and ozone-depleting gases, such as CFCs, are briefly discussed. The motivation for this was to cover flue gases from combustion as well as fuel gases from gasification processes, using various types of furnaces and boilers, and to extend the range of chemical compounds to those found in the product gases in waste incineration and energy-from- waste processes. Finally, not only 'cold' gas cleaning but also 'hot' gas cleaning is addressed. All this in an attempt to cover the wide spectrum of pollutants found in gas streams in modern thermal power generation processes, being based on combustion or gasification, with a fossil fuel, biomass or waste-derived fuel as input. Recovery boilers for black liquor are, however, not specifically-dealt with. Updates of the textbook has been produced and will also be so in future chapter by chapter. For the third edition, tine latest emission standards data for SO{sub x}, NO{sub x} and
Fundamentals of charged particle transport in gases and condensed matter
Robson, Robert E; Hildebrandt, Malte
This book offers a comprehensive and cohesive overview of transport processes associated with all kinds of charged particles, including electrons, ions, positrons, and muons, in both gases and condensed matter. The emphasis is on fundamental physics, linking experiment, theory and applications. In particular, the authors discuss: The kinetic theory of gases, from the traditional Boltzmann equation to modern generalizations A complementary approach: Maxwell's equations of change and fluid modeling Calculation of ion-atom scattering cross sections Extension to soft condensed matter, amorphous materials Applications: drift tube experiments, including the Franck-Hertz experiment, modeling plasma processing devices, muon catalysed fusion, positron emission tomography, gaseous radiation detectors Straightforward, physically-based arguments are used wherever possible to complement mathematical rigor.
Noble Gases in Lakes and Ground Waters
Kipfer, Rolf; Aeschbach-Hertig, Werner; Peeters, Frank; Stute, Marvin
In contrast to most other fields of noble gas geochemistry that mostly regard atmospheric noble gases as 'contamination,' air-derived noble gases make up the far largest and hence most important contribution to the noble gas abundance in meteoric waters, such as lakes and ground waters. Atmospheric noble gases enter the meteoric water cycle by gas partitioning during air / water exchange with the atmosphere. In lakes and oceans noble gases are exchanged with the free atmosphere at the surface...
C4N3H monolayer: A two-dimensional organic Dirac material with high Fermi velocity
Pan, Hongzhe; Zhang, Hongyu; Sun, Yuanyuan; Li, Jianfu; Du, Youwei; Tang, Nujiang
Searching for two-dimensional (2D) organic Dirac materials, which have more adaptable practical applications compared with inorganic ones, is of great significance and has been ongoing. However, only two such materials with low Fermi velocity have been discovered so far. Herein, we report the design of an organic monolayer with C4N3H stoichiometry that possesses fascinating structure and good stability in its free-standing state. More importantly, we demonstrate that this monolayer is a semimetal with anisotropic Dirac cones and very high Fermi velocity. This Fermi velocity is roughly one order of magnitude larger than the largest velocity ever reported in 2D organic Dirac materials, and it is comparable to that in graphene. The Dirac states in this monolayer arise from the extended π -electron conjugation system formed by the overlapping 2 pz orbitals of carbon and nitrogen atoms. Our finding paves the way to a search for more 2D organic Dirac materials with high Fermi velocity.
Controlling interactions between highly magnetic atoms with Feshbach resonances.
Kotochigova, Svetlana
This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic (7)S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.
Landfill gases and some effects on vegetation
Franklin B. Flower; Ida A. Leone; Edward F. Gilman; John J. Arthur
Gases moving from refuse landfills through soil were studied in New Jersey. The gases, products of anaerobic decomposition of organic matter in the refuse, caused injury and death of peach trees, ornamentals, and commercial farm crops, and create possible hazards to life and property because of the entrance of combustible gases into residences. Remedial measures are...
Theoretical Insight into Shocked Gases
Energy Technology Data Exchange (ETDEWEB)
Leiding, Jeffery Allen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
I present the results of statistical mechanical calculations on shocked molecular gases. This work provides insight into the general behavior of shock Hugoniots of gas phase molecular targets with varying initial pressures. The dissociation behavior of the molecules is emphasized. Impedance matching calculations are performed to determine the maximum degree of dissociation accessible for a given flyer velocity as a function of initial gas pressure.
Phase operators and blurring time of a pair-condensed Fermi gas
Kurkjian, H.; Castin, Y.; Sinatra, A.
Due to atomic interactions and dispersion in the total atom number, the order parameter of a pair-condensed Fermi gas experiences a collapse in a time that we derive microscopically. As in the bosonic case, this blurring time depends on the derivative of the gas chemical potential with respect to the atom number and on the variance of that atom number. The result is obtained first using linearized time-dependent Bogoliubov-de Gennes equations, then in the random-phase approximation, and then it is generalized to beyond the mean field. In this framework, we construct and compare two phase operators for the paired fermionic field: The first one, issuing from our study of the dynamics, is the infinitesimal generator of adiabatic translations in the total number of pairs. The second one is the phase operator of the amplitude of the field of pairs on the condensate mode. We explain that these two operators differ due to the dependence of the condensate wave function on the atom number.
Leggett-Garg inequalities violation via the Fermi contact hyperfine interaction
Energy Technology Data Exchange (ETDEWEB)
Lobejko, Marcin; Dajka, Jerzy [Institute of Physics, University of Silesia, Katowice (Poland); Silesian Center for Education and Interdisciplinary Research, University of Silesia, Chorzow (Poland)
In this paper we examine theoretically how the spin-spin interaction between a nuclei and an electron in the atom affects violation of the Leggett-Garg inequalities. We consider the simplest case of atoms in the {sup 2}S{sub 1/2} state that in the valence shell have just a single electron and the evolution in time of the spin is dictated only by the Fermi contact hyperfine interaction. We found that for special initial conditions and a particular measured observable the high spin nucleus couple to the valence electron such that violation of Leggett-Garg inequalities increases with total spin of states. Consequently, our results show that for the Hydrogen, the smallest atom in Nature, the violation of the Leggett-Garg inequalities is the smallest whereas for the largest atom, the Cesium, the violation is the largest. Moreover, this violation does not depend on a principal quantum number, thus our model can be used for Rydberg atoms in order to test macrorealism for 'almost macroscopic' objects. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Computational code in atomic and nuclear quantum optics: Advanced computing multiphoton resonance parameters for atoms in a strong laser field
Glushkov, A. V.; Gurskaya, M. Yu; Ignatenko, A. V.; Smirnov, A. V.; Serga, I. N.; Svinarenko, A. A.; Ternovsky, E. V.
The consistent relativistic energy approach to the finite Fermi-systems (atoms and nuclei) in a strong realistic laser field is presented and applied to computing the multiphoton resonances parameters in some atoms and nuclei. The approach is based on the Gell-Mann and Low S-matrix formalism, multiphoton resonance lines moments technique and advanced Ivanov-Ivanova algorithm of calculating the Green's function of the Dirac equation. The data for multiphoton resonance width and shift for the Cs atom and the 57Fe nucleus in dependence upon the laser intensity are listed.
Entanglement rules for holographic Fermi surfaces
Directory of Open Access Journals (Sweden)
Dibakar Roychowdhury
Full Text Available In this paper, based on the notion of Gauge/Gravity duality, we explore the laws of entanglement thermodynamics for most generic classes of Quantum Field Theories with hyperscaling violation. In our analysis, we note that for Quantum Field Theories with compressible quark like excitation, the first law of entanglement thermodynamics gets modified due to the presence of an additional term that could be identified as the entanglement chemical potential associated with hidden Fermi surfaces of the boundary theory. Most notably, we find that the so called entanglement chemical potential does not depend on the size of the entangling region and is purely determined by the quark d.o.f. encoded within the entangling region.
Adaptationism fails to resolve Fermi's paradox
Directory of Open Access Journals (Sweden)
Ćirković Milan M.
Full Text Available One of the most interesting problems in the nascent discipline of astrobiology is more than half-century old Fermi's paradox: why, considering extraordinary young age of Earth and the Solar System in the Galactic context, don't we perceive much older intelligent communities or signposts of their activity? In spite of a vigorous research activity in recent years, especially bolstered by successes of astrobiology in finding extrasolar planets and extremophiles, this problem (also known as the "Great Silence" or "astrosociological" paradox remains as open as ever. In a previous paper, we have discussed a particular evolutionary solution suggested by Karl Schroeder based on the currently dominant evolutionary doctrine of adaptationism. Here, we extend that discussion with emphasis on the problems such a solution is bound to face, and conclude that it is ultimately quite unlikely. .
Thompson, David
Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.
Ultracold atoms for precision measurement of fundamental physical quantities
CERN. Geneva
Cooling and trapping of neutral atoms has been one of the most active fields of research in physics in recent years. Several methods were demonstrated to reach temperatures as low as a few nanokelvin allowing, for example, the investigation of quantum degenerate gases. The ability to control the quantum degrees of freedom of atoms opens the way to applications for precision measurement of fundamental physical quantities. Experiments in progress, planned or being considered using new quantum devices based on ultracold atoms, namely atom interferometers and atomic clocks, will be discussed.
Loring, FH
Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec
[A possible molecular mechanism of the narcotic action of noble gases].
Dovgusha, V V; Fok, M V; Zaritskaia, G A
A molecular mechanism of the narcotic action of noble gases is suggested, which is based on the fact that noble gas atoms change the orientation of water molecules absorbed on the surface of axon membrane. The resulting change in the transmembrane potential deteriorates the propagation of nerve pulse.
All about Solids, Liquids & Gases. Physical Science for Children[TM]. Schlessinger Science Library. [Videotape].
In All About Solids, Liquids and Gases, young students will be introduced to the three common forms of matter. They'll learn that all things are made up of tiny particles called atoms and that the movement of these particles determines the form that matter takes. In solids, the particles are packed tightly together and move very little. The…
Effective oscillator strength distributions of spherically symmetric atoms for calculating polarizabilities and long-range atom–atom interactions
Energy Technology Data Exchange (ETDEWEB)
Jiang, Jun, E-mail: firstname.lastname@example.com [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Cheng, Yongjun, E-mail: firstname.lastname@example.com [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, Harbin 150080 (China); Bromley, M.W.J., E-mail: firstname.lastname@example.com [School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4075 (Australia)
Effective oscillator strength distributions are systematically generated and tabulated for the alkali atoms, the alkaline-earth atoms, the alkaline-earth ions, the rare gases and some miscellaneous atoms. These effective distributions are used to compute the dipole, quadrupole and octupole static polarizabilities, and are then applied to the calculation of the dynamic polarizabilities at imaginary frequencies. These polarizabilities can be used to determine the long-range C{sub 6}, C{sub 8} and C{sub 10} atom–atom interactions for the dimers formed from any of these atoms and ions, and we present tables covering all of these combinations.
African Journals Online (AJOL)
Atomic Power. By Denis Taylor: Dr. Taylor was formerly Chief UNESCO Advisor at the University. College, Nairobi, Kenya and is now Professor of Electrical Engineering in the Uni- versity of ... method of producing radioactive isotopes, which are materials .... the sealing and the pressure balancing, all can be carried out ...
Mechanics of liquids and gases
Loitsyanskii, L G; Jones, W P
Mechanics of Liquids and Gases, Second Edition is a 10-chapter text that covers significant revisions concerning the dynamics of an ideal gas, a viscous liquid and a viscous gas.After an expanded introduction to the fundamental properties and methods of the mechanics of fluids, this edition goes on dealing with the kinetics and general questions of dynamics. The next chapters describe the one-dimensional pipe flow of a gas with friction, the elementary theory of the shock tube; Riemann's theory of the wave propagation of finite intensity, and the theory of plane subsonic and supersonic flows.
Ultrasonic waves in classical gases
Magner, A. G.; Gorenstein, M. I.; Grygoriev, U. V.
The velocity and absorption coefficient for the plane sound waves in a classical gas are obtained by solving the Boltzmann kinetic equation, which describes the reaction of the single-particle distribution function to a periodic external field. Within the linear response theory, the nonperturbative dispersion equation valid for all sound frequencies is derived and solved numerically. The results are in agreement with the approximate analytical solutions found for both the frequent- and rare-collision regimes. These results are also in qualitative agreement with the experimental data for ultrasonic waves in dilute gases.
X.509 Authentication/Authorization in FermiCloud
Energy Technology Data Exchange (ETDEWEB)
Kim, Hyunwoo [Fermilab; Timm, Steven [Fermilab
We present a summary of how X.509 authentication and authorization are used with OpenNebula in FermiCloud. We also describe a history of why the X.509 authentication was needed in FermiCloud, and review X.509 authorization options, both internal and external to OpenNebula. We show how these options can be and have been used to successfully run scientific workflows on federated clouds, which include OpenNebula on FermiCloud and Amazon Web Services as well as other community clouds. We also outline federation options being used by other commercial and open-source clouds and cloud research projects.
Visualizing the influence of the Fermi surface on superconductivity
Herrera Vasco, Edwin
Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de la Materia Condensada. Fecha de lectura: 15-12-2016 IN the book of Kittel, a well-known citation attributed to Mackintosh states that metals are "a solid with a Fermi surface". When metals become superconducting, BCS theory tells us that a gap opens at the Fermi level, so that all electronic states at the Fermi surface are lost. The shape and the properties of electro...
Fermi Large Area Telescope Bright Gamma-ray Source List
Energy Technology Data Exchange (ETDEWEB)
Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /KIPAC, Menlo Park /SLAC; Ajello, M.; /KIPAC, Menlo Park /SLAC; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U., OKC /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Band, D.L.; /NASA, Goddard /NASA, Goddard; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bastieri, Denis; /INFN, Padua /Padua U.; Bechtol, K.; /KIPAC, Menlo Park /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /KIPAC, Menlo Park /SLAC; Bignami, G.F.; /Pavia U.; Bloom, Elliott D.; /KIPAC, Menlo Park /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /KIPAC, Menlo Park /SLAC; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle /Bari U. /INFN, Bari /KIPAC, Menlo Park /SLAC /IASF, Milan /IASF, Milan /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /KIPAC, Menlo Park /SLAC /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /KIPAC, Menlo Park /SLAC /INFN, Perugia /Perugia U. /KIPAC, Menlo Park /SLAC /Montpellier U. /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /KIPAC, Menlo Park /SLAC /ASDC, Frascati /NASA, Goddard /Maryland U. /Naval Research Lab, Wash., D.C. /INFN, Trieste /Pavia U. /Bari U. /INFN, Bari /KIPAC, Menlo Park /SLAC /UC, Santa Cruz /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /NASA, Goddard; /more authors..
Following its launch in 2008 June, the Fermi Gamma-ray Space Telescope (Fermi) began a sky survey in August. The Large Area Telescope (LAT) on Fermi in three months produced a deeper and better resolved map of the {gamma}-ray sky than any previous space mission. We present here initial results for energies above 100 MeV for the 205 most significant (statistical significance greater than {approx}10{sigma}) {gamma}-ray sources in these data. These are the best characterized and best localized point-like (i.e., spatially unresolved) {gamma}-ray sources in the early mission data.
Oscillating Casimir force between two slabs in a Fermi sea
DEFF Research Database (Denmark)
Li-Wei, Chen; Guo-Zhen, Su; Jin-Can, Chen
The Casimir effect for two parallel slabs immersed in an ideal Fermi sea is investigated at both zero and nonzero temperatures. It is found that the Casimir effect in a Fermi gas is distinctly different from that in an electromagnetic field or a massive Bose gas. In contrast to the familiar result...... that the Casimir force decreases monotonically with the increase of the separation L between two slabs in an electromagnetic field and a massive Bose gas, the Casimir force in a Fermi gas oscillates as a function of L. The Casimir force can be either attractive or repulsive, depending sensitively on the magnitude...
Atomic Physics 15: Proceedings of the Fifteenth International Conference on Atomic Physics.
van Linden van den Heuvell, H. B.; Walraven, J. T. M.; Reynolds, M. W.
The Table of Contents for the full book PDF is as follows: * Preface * Generation of a "Schrödinger cat" of radiation and observation of its decoherence * Synthesis of entangled states and quantum computing * Entangled states of atomic ions for quantum metrology and computation * Entanglement and indistinguishability: Coherence experiments with photon pairs and triplets * Atom optics as a testing ground for quantum chaos * Coherent ultra-bright XUV lasers and harmonics * Hollow atoms * Interdisciplinary experiments with polarized noble gases * The creation and study of Bose-Einstein condensation in a cold alkali vapor * oscopic quantum phenomena in trapped Bose-condensed gases * Doppler-free spectroscopy of trapped atomic hydrogen * QED and the ground state of helium * Towards coherent atomic samples using laser cooling * Bose-Einstein condensation of a weakly-interacting gas * Zeeman and his contemporaries: Dutch physics around 1900 * Zeeman's great discovery * The Zeeman effect: A tool for atom manipulation * The Zeeman effect a century later: New insights into classical physics * QED effects in few-electron high-Z systems * Lamb shift experiments on high-Z one- and two-electron systems * Fundamental constants of nature * Response of atoms in photonic lattices * Hydrogen-like systems and quantum electrodynamics * New experiments with atomic lattices bound by light * Bloch oscillations of atoms in an optical potential * Quantum decoherence and inertial sensing with atom interferometers * Quantum effects in He clusters * Atoms in super-intense radiation fields * Wave packet dynamics of excited atomic electrons in intense laser fields * Nonlinear laser-electron scattering * Comparing the antiproton and proton and progress toward cold antihydrogen * Author Index
Crease, Robert P.
The American composer John Adams uses opera to dramatize controversial current events. His 1987 work Nixon in China was about the landmark meeting in 1972 between US President Richard Nixon and Chairman Mao Zedong of China; The Death of Klinghoffer (1991) was a musical re-enactment of an incident in 1985 when Palestinian terrorists kidnapped and murdered a wheelchair-bound Jewish tourist on a cruise ship. Adams's latest opera, Doctor Atomic, is also tied to a controversial event: the first atomic-bomb test in Alamogordo, New Mexico, on 16 June 1945. The opera premièred in San Francisco in 2005, had a highly publicized debut at the Metropolitan Opera in New York in 2008, and will have another debut on 25 February - with essentially the same cast - at the English National Opera in London.
Energy Technology Data Exchange (ETDEWEB)
Goldschmidt, B.
This book is a memoir of rivalries among the Allies over the bomb, by a participant and observer. Nuclear proliferation began in the uneasy wartime collaboration of the United States, England, Canada, and Free France to produce the atom bomb. Through the changes of history, a young French chemist had a role in almost every act of this international drama. This memoir is based on Goldschmidt's own recollections, interviews with other leading figures, and 3,000 pages of newly declassified documents in Allied archives. From his own start as Marie Curie's lab assistant, Goldschmidt's career was closely intertwined with Frances complicated rise to membership in the nuclear club. As a refugee from the Nazis, he became part of the wartime nuclear energy project in Canada and found himself the only French scientist to work (although briefly) on the American atom bomb project.
Vortex Lattices in the Bose-Fermi Superfluid Mixture.
Jiang, Yuzhu; Qi, Ran; Shi, Zhe-Yu; Zhai, Hui
In this Letter we show that the vortex lattice structure in the Bose-Fermi superfluid mixture can undergo a sequence of structure transitions when the Fermi superfluid is tuned from the BCS regime to the BEC regime. This is due to the difference in the vortex core structure of a Fermi superfluid in the BCS regime and in the BEC regime. In the BCS regime the vortex core is nearly filled, while the density at the vortex core gradually decreases until it empties out in the BEC regime. Therefore, with the density-density interaction between the Bose and the Fermi superfluids, interaction between the two sets of vortex lattices gets stronger in the BEC regime, which yields the structure transition of vortex lattices. In view of the recent realization of this superfluid mixture and vortices therein, our theoretical predication can be verified experimentally in the near future.
GRBs in the Era of Swift and Fermi
Racusin, Judy
Utilizing both Swift and Fermi to study GRBs provides us with a unique broad spectral and temporal window into both prompt emission and afterglow studies. Swift has provided key information from GRB follow-up of LAT detected bursts) that has led to ground-based redshift measurements and afterglow broadband light curves and SEDs. We study the X-ray and optical afterglows of Fermi-LAT detected bursts in the context of the hundreds of GRBs discovered by Swift over the last 7 years) in order to better understand the origin of the high-energy gamma-rays. We also briefly describe the efforts to best facilitate joint Swift-Fermi observations. These initial results demonstrate the synergy between Swift and Fermi) and hint at the many interesting discoveries to come.
Restricting UHECRs and cosmogenic neutrinos with Fermi-LAT
National Research Council Canada - National Science Library
Berezinsky, V; Gazizov, A; Kachelrieß, M; Ostapchenko, S
...[less than or approximately equal to]100GeV. The Fermi-LAT Collaboration has recently reported a measurement of the extragalactic diffuse background finding it less intense and softer than previously measured by EGRET...
Fermi Bubble Edges: Spectrum and Diffusion Function
Keshet, Uri; Gurwich, Ilya
Current measurements of the γ-ray Fermi bubbles (FB) are based on model-dependent tracers, carry substantial systematic uncertainties, and contain some discrepancies between each other. We show that gradient filters pick out the FB edges, which are found to smoothly connect to the bipolar X-ray structure emanating from the Galactic center, thus supporting the interpretation of the FBs as a Galactic-scale phenomenon. The sharp edges facilitate a direct, model-free measurement of the peripheral FB spectrum. The result is strikingly similar to the full FB-integrated spectrum, softened by a power law of index η ≃ (0.2-0.3). This is naturally explained, in both hadronic and leptonic models, if cosmic rays are injected at the edge, and diffuse away preferentially at higher energies E. The inferred, averaged diffusion function in the (more plausible) leptonic model, D{(E)≃ {10}29.5(E/10{GeV})}0.48+/- 0.02 {{cm}}2 {{{s}}}-1, is consistent with estimates for Kraichnan-like turbulence. Our results, in particular the minute spatial variations in η, indicate that the FB edge is a strong, Mach ≳5, forward shock.
Relativistic finite-temperature Thomas-Fermi model
Faussurier, Gérald
We investigate the relativistic finite-temperature Thomas-Fermi model, which has been proposed recently in an astrophysical context. Assuming a constant distribution of protons inside the nucleus of finite size avoids severe divergence of the electron density with respect to a point-like nucleus. A formula for the nuclear radius is chosen to treat any element. The relativistic finite-temperature Thomas-Fermi model matches the two asymptotic regimes, i.e., the non-relativistic and the ultra-relativistic finite-temperature Thomas-Fermi models. The equation of state is considered in detail. For each version of the finite-temperature Thomas-Fermi model, the pressure, the kinetic energy, and the entropy are calculated. The internal energy and free energy are also considered. The thermodynamic consistency of the three models is considered by working from the free energy. The virial question is also studied in the three cases as well as the relationship with the density functional theory. The relativistic finite-temperature Thomas-Fermi model is far more involved than the non-relativistic and ultra-relativistic finite-temperature Thomas-Fermi models that are very close to each other from a mathematical point of view.
Angular correlation studies in noble gases
Coleman, P. G.
There has been a recent revival of interest in the measurement of angular correlation of annihilation photons from the decay of positrons and positronium in gases. This revival has been stimulated by the possibility offered by the technique to shed new light on the apparently low positronium formation fraction in the heavier noble gases and to provide information on positronium quenching processes in gases such as oxygen. There is also the potential for learning about positronium slowing down in gases. This review focuses on experimental noble gas work and considers what new information has been, and may be, gained from these studies.
A nebula of gases from Io surrounding Jupiter.
Krimigis, Stamatios M; Mitchell, Donald G; Hamilton, Douglas C; Dandouras, Jannis; Armstrong, Thomas P; Bolton, Scott J; Cheng, Andrew F; Gloeckler, George; Hsieh, K C; Keath, Edwin P; Krupp, Norbert; Lagg, Andreas; Lanzerotti, Louis J; Livi, Stefano; Mauk, Barry H; McEntire, Richard W; Roelof, Edmond C; Wilken, Berend; Williams, Donald J
Several planetary missions have reported the presence of substantial numbers of energetic ions and electrons surrounding Jupiter; relativistic electrons are observable up to several astronomical units (au) from the planet. A population of energetic (>30[?]keV) neutral particles also has been reported, but the instrumentation was not able to determine the mass or charge state of the particles, which were subsequently labelled energetic neutral atoms. Although images showing the presence of the trace element sodium were obtained, the source and identity of the neutral atoms---and their overall significance relative to the loss of charged particles from Jupiter's magnetosphere---were unknown. Here we report the discovery by the Cassini spacecraft of a fast (>103[?]km[?]s-1) and hot magnetospheric neutral wind extending more than 0.5[?]au from Jupiter, and the presence of energetic neutral atoms (both hot and cold) that have been accelerated by the electric field in the solar wind. We suggest that these atoms originate in volcanic gases from Io, undergo significant evolution through various electromagnetic interactions, escape Jupiter's magnetosphere and then populate the environment around the planet. Thus a 'nebula' is created that extends outwards over hundreds of jovian radii.
Biological effects of noble gases.
Růzicka, J; Benes, J; Bolek, L; Markvartová, V
Noble gases are known for their inertness. They do not react chemically with any element at normal temperature and pressure. Through that, some of them are known to be biologically active by their sedative, hypnotic and analgesic properties. Common inhalation anesthetics are characterized by some disadvantages (toxicity, decreased cardiac output, etc). Inhalation of xenon introduces anesthesia and has none of the above disadvantages, hence xenon seems to be the anesthetic gas of the future (with just one disadvantage - its cost). It is known that argon has similar anesthetic properties (under hyperbaric conditions), which is much cheaper and easily accessible. The question is if this could be used in clinical practice, in anesthesia of patients who undergo treatment in the hyperbaric chamber. Xenon was found to be organ-protective. Recent animal experiments indicated that xenon decreases infarction size after ischemic attack on brain or heart. The goal of our study is to check if hyperbaric argon has properties similar to those of xenon.
Busey, H.M.
A convection type recombiner is described for catalytically recombining hydrogen and oxygen which have been radiolytically decomposed in an aqueous homogeneous nuclear reactor. The device is so designed that the energy of recombination is used to circulate the gas mixture over the catalyst. The device consists of a vertical cylinder having baffles at its lower enda above these coarse screens having platinum and alumina pellets cemented thereon, and an annular passage for the return of recombined, condensed water to the reactor moderator system. This devicea having no moving parts, provides a simple and efficient means of removing the danger of accumulated hot radioactive, explosive gases, and restoring them to the moderator system for reuse.
Temporal dynamics of Bose-condensed gases
Energy Technology Data Exchange (ETDEWEB)
Trujillo Martinez, Mauricio
We perform a detailed quantum dynamical study of non-equilibrium trapped, interacting Bose-condensed gases. We investigate Josephson oscillations between interacting Bose-Einstein condensates confined in a finite size double-well trap and the non-trivial time evolution of a coherent state placed at the center of a two dimensional optical lattice. For the Josephson oscillations three time scales appear. We find that Josephson junction can sustain multiple undamped oscillations up to a characteristic time scale τ{sub c} without exciting atoms out of the condensates. Beyond the characteristic time scale τ{sub c} the dynamics of the junction are governed by fast, non-condensed particles assisted Josephson tunnelling as well as the collisions between non-condensed particles. In the non-condensed particles dominated regime we observe strong damping of the oscillations due to inelastic collisions, equilibrating the system leading to an effective loss of details of the initial conditions. In addition, we predict that an initially self-trapped BEC state will be destroyed by these fast dynamics. The time evolution of a coherent state released at the center of a two dimensional optical lattice shows a ballistic expansion with a decreasing expansion velocity for increasing two-body interactions strength and particle number. Additionally, we predict that if the two-body interactions strength exceeds a certain value, a forerunner splits up from the expanding coherent state. We also observe that this system, which is prepared far from equilibrium, can evolve to a quasistationary non-equilibrium state.
An Introduction to Atomic Layer Deposition
Dwivedi, Vivek H.
Atomic Layer Deposition has been instrumental in providing a deposition method for multiple space flight applications. It is well known that ALD is a cost effective nanoadditive-manufacturing technique that allows for the conformal coating of substrates with atomic control in a benign temperature and pressure environment. Through the introduction of paired precursor gases, thin films can be deposited on a myriad of substrates from flat surfaces to those with significant topography. By providing atomic layer control, where single layers of atoms can be deposited, the fabrication of metal transparent films, precise nano-laminates, and coatings of nano-channels, pores and particles is achievable. The feasibility of this technology for NASA line of business applications range from thermal systems, optics, sensors, to environmental protection. An overview of this technology will be presented.
Low-temperature structure and Fermi surface of (La,Ce)TiGe{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Foerster, Tobias; Grasemann, Jacob; Uhlarz, Marc; Wosnitza, Jochen [Dresden High Magnetic Field Laboratory (HLD), Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Rosner, Helge; Stockert, Oliver [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Kittler, Wolfram; Loehneysen, Hilbert von [Karlsruhe Institute of Technology, Karlsruhe (Germany); Fritsch, Veronika [Institut fuer Physik, Universitaet Augsburg, Augsburg (Germany)
CeTiGe{sub 3} presents the rare case of a ferromagnetically (T{sub C} ∼ 14 K) ordered Kondo-lattice compound and is probably the first known example of an intermetallic hexagonal perovskite of the BaNiO{sub 3} structure type. LaTiGe{sub 3} may be used as its nonmagnetic reference, since both compounds crystallize in the same crystal structure. To clarify the interplay between structural, localized, and itinerant degrees of freedom an accurate knowledge of the electronic band structure is necessary. Here, we present a detailed electronic-structure study of both compounds applying full potential density functional calculations. Since the Ge's atomic position couples strongly to the band structure at the Fermi energy, a low-temperature, high-resolution structure refinement was made. We attempt to separate the influence of different parameters on the topology of the respective Fermi surfaces and will compare our results with de Haas-van Alphen measurements.
Applied atomic and collision physics special topics
Massey, H S W; Bederson, Benjamin
Applied Atomic Collision Physics, Volume 5: Special Topics deals with topics on applications of atomic collisions that were not covered in the first four volumes of the treatise. The book opens with a chapter on ultrasensitive chemical detectors. This is followed by separate chapters on lighting, magnetohydrodynamic electrical power generation, gas breakdown and high voltage insulating gases, thermionic energy converters, and charged particle detectors. Subsequent chapters deal with the operation of multiwire drift and proportional chambers and streamer chambers and their use in high energy p
High mobility two-dimensional hole gases in GaAs/AlGaAs heterostructures; Hochbewegliche zweidimensionale Lochsysteme in GaAs/AlGaAs Heterostrukturen
Energy Technology Data Exchange (ETDEWEB)
Gerl, Christian
This thesis outlines the fabrication of high mobility two-dimensional hole-gases (2DHG) in GaAs/AlGaAs heterostructures with molecular beam epitaxy (MBE) and their characterization with magnetotransport measurements at low temperatures between 4 K and 30 mK. Here the optimization of the carrier mobility is focused. This will be achieved by introducing a novel carbon-filament doping source, with which contaminations of the MBE system and therefore in the grown layers can be reduced and by vary the band structure design to minimize scattering processes. With the help of these actions, hole mobilities above 1 E6 cm{sup 2}/Vs are achievable, what reflects an increase of factor 3 in the (001)- and factor 6.5 in the (110)- oriented transport plane compared to common 2DHGs. Furthermore states of the fractional Quantum Hall Effect can be observed in these 2DHGs, only visible in n-doped 2D systems so fare. Magnetotransport measurements on 2DHGs with aluminum gates reveal a hysteretic behavior of the carrier density with respect to the gate potential which can be attributed to the incorporation mechanisms of carbon atoms as acceptor. Temperature dependent magnetotransport measurements allow the evaluation of effective mass and quantum scattering time as well as the dependence of these parameters from the band structure design. In these experiments an aperiodic behavior of the Shubnikov-de Haas oscillations can be observed in the inverse magnetic field, which is attributed to the position of the fermi energy in the immediate vicinity of crossing regions of the complex Landau fan of 2DHGs. (orig.)
Pairing in Fermi Fluids in Restricted Geometries
Bashkin, Eugene P.; Wojdylo, John
We consider dimerization of 3He in a dilute solution of 3He in superfluid 4He filling narrow channels of a kind typically found in nanoscale porous media. Dimer formation is facilitated by the one dimensional geometry and occurs despite the fact that the interparticle interaction is too weak to lead to a bound state in bulk fluid. At sufficiently low temperatures, dimerization results in the effective "bosonization" of the system: a Bose quantum fluid of (3He)2 arises in place of the 3He Fermi component. At sufficiently high temperatures, for which the 3He impurity quasiparticles form a Maxwell-Boltzmann gas, the thermodynamics is significantly affected by the presence of dimers. In particular, the specific heat and magnetic susceptibility of the 3He component show a marked deviation from behaviour expected if dimers were absent. Solution of the Schrödinger equation for a smooth cylindrical pore indicates that the binding energy in straight nanoscale channels ought to be of sufficiently high magnitude to make experimental observation feasible. The presence of (3He)2 dimers gives rise to an extra absorption mechanism for first sound propagating through the superfluid 4He, due to resonant absorption and decay of dimers in the acoustic field. We have calculated the absorption coefficient. Several experiments suggest themselves, utilizing, perhaps, K-L zeolites or carbon nanotubes. If the dimers themselves turn out to be attractive, then quadrumers may appear: it may even be the case that a single 3He polymer will form over the entire length of the channel.
Statistical properties of Fermi GBM GRBs' spectra
Rácz, István I.; Balázs, Lajos G.; Horvath, Istvan; Tóth, L. Viktor; Bagoly, Zsolt
Statistical studies of gamma-ray burst (GRB) spectra may result in important information on the physics of GRBs. The Fermi GBM catalogue contains GRB parameters (peak energy, spectral indices, and intensity) estimated fitting the gamma-ray spectral energy distribution of the total emission (fluence, flnc), and during the time of the peak flux (pflx). Using contingency tables, we studied the relationship of the models best-fitting pflx and flnc time intervals. Our analysis revealed an ordering of the spectra into a power law - Comptonized - smoothly broken power law - Band series. This result was further supported by a correspondence analysis of the pflx and flnc spectra categorical variables. We performed a linear discriminant analysis (LDA) to find a relationship between categorical (spectral) and model independent physical data. LDA resulted in highly significant physical differences among the spectral types, that is more pronounced in the case of the pflx spectra, than for the flnc spectra. We interpreted this difference as caused by the temporal variation of the spectrum during the outburst. This spectral variability is confirmed by the differences in the low-energy spectral index and peak energy, between the pflx and flnc spectra. We found that the synchrotron radiation is significant in GBM spectra. The mean low-energy spectral index is close to the canonical value of α = -2/3 during the peak flux. However, α is ˜ -0.9 for the spectra of the fluences. We interpret this difference as showing that the effect of cooling is important only for the fluence spectra.
40 CFR 1065.750 - Analytical gases.
... ± 3.0% of the NIST-accepted value or other similar standards we approve, and meet the stability..., such as a compressed-gas cylinder. (d) To maintain stability and purity of gas standards, use good..., span, and calibration gases. For example, it may be necessary to store bottles of condensable gases in...
Properties and Bibliography of GaSe
Brahim-Otsmane 1993) and (Fargues 1993). Growth of Fullerene thin films on a GaSe substrate is covered by (Sakurai 1993). There is some literature on the...and GaSe samples." Experimentelle Technik der Physik. 37 173-185 Stadnik, V. A. (1988). "Optical bistability, the pulsation effect, and 95 GaS. Page 55
Greenhouse Gases Concentrations in the Atmosphere Along ...
African Journals Online (AJOL)
This study investigated effect of vehicular emission on greenhouse gases concentrations along selected roads of different traffic densities in Abeokuta, Ogun State, Nigeria. Nine roads comprised highway, commercial and residential were selected. Greenhouse Gases (GHGs) were determined from both sides of the roads by ...
40 CFR 90.312 - Analytical gases.
... calibration gas must not exceed five percent of the NO content); CO2 and purified nitrogen. Note: For the HFID... accuracy of the mixing device must be such that the concentration of the diluted gases may be determined to... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Analytical gases. 90.312 Section 90...
Calculation of thermodynamic corrections from electronic exchange effects in Thomas–Fermi model employed for hot dense plasma
Directory of Open Access Journals (Sweden)
H Hosseinkhani
Full Text Available In this paper, considering the plasma electronic exchange intraction effects, first, Thomas–Fermi equation has been solved numerically. Then, employing the results of these equations, the amount of exchange corrections for pressure and internal energy of the plasma (electron gas with specific atomic number has been calculated based on variation of plasma density and temperature. The results of the calculations can be used in both quantitative and qualitative description of changing the phase of matter in high temperature and density, encountered with in theoretical and experimental studies of inertial fusion and astro physical phenomena as well.
Hyperpolarized noble gases as contrast agents.
Zhou, Xin
Hyperpolarized noble gases ((3)He and (129)Xe) can provide NMR signal enhancements of 10,000 to 100,000 times that of thermally polarized gases and have shown great potential for applications in lung magnetic resonance imaging (MRI) by greatly enhancing the sensitivity and contrast. These gases obtain a highly polarized state by employing a spin exchange optical pumping technique. In this chapter, the underlying physics of spin exchange optical pumping for production of hyperpolarized noble gases is explained and the basic components and procedures for building a polarizer are described. The storage and delivery strategies of hyperpolarized gases for in vivo imaging are discussed. Many of the problems that are likely to be encountered in practical experiments and the corresponding detailed approaches to overcome them are also discussed.
Magnetic correlations in the two-dimensional repulsive Fermi-Hubbard model
Šimkovic, Fedor; Deng, Youjin; Prokof'ev, N. V.; Svistunov, B. V.; Tupitsyn, I. S.; Kozik, Evgeny
The repulsive Fermi-Hubbard model on a square lattice has a rich phase diagram near half-filling (n =1 ): at n =1 the ground state is an antiferromagnetic insulator, at 0.6
Indications of Bose-Einstein condensation and Fermi quenching in the decay of hot nuclei
Marini, P.; Zheng, H.; Bonasera, A.; Verde, , G.; Chbihi, A.
We report experimental signals of Bose-Einstein condensation and Fermi quenching in nuclear systems at low excitation energies produced in {^{40}Ca}+{^{40}Ca} collisions. The innovative experimental setup, constituted by the coupling of the VAMOS spectrometer to the 4π charged particle detector INDRA, allowed us to reconstruct the characteristics of the decaying hot source. We have investigated the thermodynamic properties, temperatures and partial nucleon densities, of the low density region of the nuclear system with quantum fluctuation analysis techniques, as "seen" by bosons and fermions separately. We show that in dilute hot nuclear systems, as in atomic traps, bosons experience a higher density than fermions do. Also, the nuclear interaction between fermions and bosons does not significantly reduce the fermion quenching and the Bose condensation.
Seebeck effect at the atomic scale.
Lee, Eui-Sup; Cho, Sanghee; Lyeo, Ho-Ki; Kim, Yong-Hyun
The atomic variations of electronic wave functions at the surface and electron scattering near a defect have been detected unprecedentedly by tracing thermoelectric voltages given a temperature bias [Cho et al., Nat. Mater. 12, 913 (2013)]. Because thermoelectricity, or the Seebeck effect, is associated with heat-induced electron diffusion, how the thermoelectric signal is related to the atomic-scale wave functions and what the role of the temperature is at such a length scale remain very unclear. Here we show that coherent electron and heat transport through a pointlike contact produces an atomic Seebeck effect, which is described by the mesoscopic Seebeck coefficient multiplied by an effective temperature drop at the interface. The mesoscopic Seebeck coefficient is approximately proportional to the logarithmic energy derivative of local density of states at the Fermi energy. We deduced that the effective temperature drop at the tip-sample junction could vary at a subangstrom scale depending on atom-to-atom interaction at the interface. A computer-based simulation method of thermoelectric images is proposed, and a point defect in graphene was identified by comparing experiment and the simulation of thermoelectric imaging.
Atomic color superfluid via three-body loss.
Kantian, A; Dalmonte, M; Diehl, S; Hofstetter, W; Zoller, P; Daley, A J
Large three-body loss rates in a three-component Fermi gas confined in an optical lattice can dynamically prevent atoms from tunneling so as to occupy a lattice site with three atoms. This effective constraint not only suppresses the occurrence of actual loss events, but stabilizes BCS-pairing phases by suppressing the formation of trions. We study the effect of the constraint on the many-body physics using bosonization and density matrix renormalization group techniques, and also investigate the full dissipative dynamics including loss for the example of 6Li.
Anisotropic behavior and inhomogeneity of atomic local densities of states in graphene with vacancy groups
Directory of Open Access Journals (Sweden)
V.V. Eremenko
Full Text Available The electron local density of states (LDOS are calculated for graphene with isolated vacancies, divacancies and vacancy group of four nearest-neighbor vacancies. A strong anisotropy of behavior of LDOS near Fermi level is demonstrated for atoms near defect. Effect of next-to-nearest neighbor interaction on the properties of graphene with vacancies is established.
A simple model for atomic layer doped field-effect transistor (ALD-FET) electronic states
Energy Technology Data Exchange (ETDEWEB)
Mora R, M.E. [Centro de Investigaciones en Optica, Unidad Aguascalientes. Juan de Montoro 207, Zona Centro, 20000 Aguascalientes (Mexico); Gaggero S, L.M. [Escuela de Fisica, Universidad Autonoma de Zacatecas, Av. Preparatoria 301, 98060 Zacatecas (Mexico)
We propose a simple potential model based on the Thomas-Fermi approximation to reproduce the main properties of the electronic structure of an atomic layer doped field effect transistor. Preliminary numerical results for a Si-based ALD-FET justify why bound electronic states are not observed in the experiment. (Author)
Establishing a Consistent Theory of Transport in Strongly Correlated Fermi Superfluids
Boyack, Rufus M.
A diagrammatic method of obtaining exact gauge-invariant response functions in strongly correlated Fermi superfluids is implemented for several example condensed matter systems of current interest. These include: topological superfluids, high temperature superconductors, and superfluids with finite center-of-mass momentum pairing known as Fulde-Ferrell superfluids. Much of the literature on these systems has focused on single-particle properties or alternatively has invoked simple approximations to treat response functions. The goal is to show that, for this wide class of topical problems, one can compute exact response functions. This enables assessment of the validity of different physical scenarios and allows a very broad class of experiments to be addressed. The method developed is based on deriving the full electromagnetic vertex, which satisfies the Ward-Takahashi identity, and determining the collective modes in a manner compatible with the self-consistent gap equation. In the condensed phase of a superfluid and a superconductor, where gauge invariance is spontaneously broken, it is crucial to determine the collective modes from the gap equation in a manner which restores gauge invariance. Our diagrammatic framework provides a very general and powerful method for obtaining these collective modes in a variety of strongly correlated Fermi superfluids. We show that a full electromagnetic vertex satisfying the Ward-Takahashi identity ensures the f-sum rule is satisfied and thus charge is conserved. This diagrammatic method is implemented for both normal and superfluid phases. While there are no collective modes in the normal phase, the Ward-Takahashi identity plays a similarly important role. In particular, for the normal phase we study Rashba spin-orbit coupled Fermi gases with intrinsic pairing in the absence and presence of a magnetic field. Exact density and spin response functions are obtained, even in the absence of a spin conservation law, providing
Equilibrium vortex lattices of a binary rotating atomic Bose–Einstein condensate with unequal atomic masses
Energy Technology Data Exchange (ETDEWEB)
Dong, Biao; Wang, Lin-Xue; Chen, Guang-Ping [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi'an 710600 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Han, Wei; Zhang, Shou-Gang [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi'an 710600 (China); Zhang, Xiao-Fei, E-mail: email@example.com [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi'an 710600 (China)
We perform a detailed numerical study of the equilibrium ground-state structures of a binary rotating Bose–Einstein condensate with unequal atomic masses. Our results show that the ground-state distribution and its related vortex configurations are complex events that differ markedly depending strongly on the strength of rotation frequency, as well as on the ratio of atomic masses. We also discuss the structures and radii of the clouds, the number and the size of the core region of the vortices, as a function of the rotation frequency, and of the ratio of atomic masses, and the analytical results agree well with our numerical simulations. This work may open an alternate way in the quantum control of the binary rotating quantum gases with unequal atomic masses. - Highlights: • A binary quantum gases with unequal atomic masses is considered. • Effects of the ratio of atomic masses and rotation frequency are discussed in full parameter space. • The detailed information about both the cloud and vortices are also discussed.
Pomeranchuk instability in a non-Fermi liquid from holography
Edalati, Mohammad; Lo, Ka Wai; Phillips, Philip W.
The Pomeranchuk instability, in which an isotropic Fermi surface distorts and becomes anisotropic due to strong interactions, is a possible mechanism for the growing number of experimental systems which display transport properties that differ along the x and y axes. We show here that the gauge-gravity duality can be used to describe such an instability in fermionic systems. Our holographic model consists of fermions in a background which describes the causal propagation of a massive neutral spin-two field in an asymptotically anti-de Sitter spacetime. The Fermi surfaces in the boundary theory distort spontaneously and become anisotropic once the neutral massive spin-two field develops a normalizable mode in the bulk. Analysis of the fermionic correlators reveals that the low-lying fermionic excitations are non-Fermi liquidlike both before and after the Fermi surface shape distortion. Further, the spectral weight along the Fermi surface is angularly dependent and can be made to vanish along certain directions.
Tuning the Fano factor of graphene via Fermi velocity modulation
Lima, Jonas R. F.; Barbosa, Anderson L. R.; Bezerra, C. G.; Pereira, Luiz Felipe C.
In this work we investigate the influence of a Fermi velocity modulation on the Fano factor of periodic and quasi-periodic graphene superlattices. We consider the continuum model and use the transfer matrix method to solve the Dirac-like equation for graphene where the electrostatic potential, energy gap and Fermi velocity are piecewise constant functions of the position x. We found that in the presence of an energy gap, it is possible to tune the energy of the Fano factor peak and consequently the location of the Dirac point, by a modulation in the Fermi velocity. Hence, the peak of the Fano factor can be used experimentally to identify the Dirac point. We show that for higher values of the Fermi velocity the Fano factor goes below 1/3 at the Dirac point. Furthermore, we show that in periodic superlattices the location of Fano factor peaks is symmetric when the Fermi velocity vA and vB is exchanged, however by introducing quasi-periodicity the symmetry is lost. The Fano factor usually holds a universal value for a specific transport regime, which reveals that the possibility of controlling it in graphene is a notable result.
Pacifying the Fermi-liquid: battling the devious fermion signs
Directory of Open Access Journals (Sweden)
J. Zaanen
Full Text Available The fermion sign problem is studied in the path integral formalism. The standard picture of Fermi liquids is first critically analyzed, pointing out some of its rather peculiar properties. The insightful work of Ceperley in constructing fermionic path integrals in terms of constrained world-lines is then reviewed. In this representation, the minus signs associated with Fermi-Dirac statistics are self consistently translated into a geometrical constraint structure (the nodal hypersurface acting on an effective bosonic dynamics. As an illustrative example we use this formalism to study 1+1-dimensional systems, where statistics are irrelevant, and hence the sign problem can be circumvented. In this low-dimensional example, the structure of the nodal constraints leads to a lucid picture of the entropic interaction essential to one-dimensional physics. Working with the path integral in momentum space, we then show that the Fermi gas can be understood by analogy to a Mott insulator in a harmonic trap. Going back to real space, we discuss the topological properties of the nodal cells, and suggest a new holographic conjecture relating Fermi liquids in higher dimensions to soft-core bosons in one dimension. We also discuss some possible connections between mixed Bose/Fermi systems and supersymmtery.
High Atom Number in Microsized Atom Traps
Final Performance Report on ONR Grant N00014-12-1-0608 High atom number in microsized atom traps for the period 15 May 2012 through 14 September...TYPE Final Technical Report 3. DATES COVERED (From - To) 05/15/2012-09/14/2012 4. TITLE AND SUBTITLE High atom number in microsized atom traps...forces for implementing a small-footprint, large-number atom -chip instrument. Bichromatic forces rely on absorption and stimulated emission to produce
Quantum Monte Carlo simulations of the Fermi-polaron problem and bosons with Gaussian interactions
Energy Technology Data Exchange (ETDEWEB)
Kroiss, Peter Michael
This thesis deals with the application of current Quantum Monte Carlo algorithms to many-body systems of fermionic and bosonic species. The first part applies the diagrammatic Monte Carlo method to the Fermi polaron problem, a system of an impurity interacting resonantly with a homogeneous Fermi bath. It is numerically shown that the three particle-hole diagrams do not contribute significantly to the final answer in a quasi-two-dimensional setup, thus demonstrating a nearly perfect destructive interference of contributions in subspaces with higher-order particle-hole lines. Consequently, for strong-enough confinement in the third direction, the transition between the polaron and the molecule ground state is found to be in good agreement with the pure two-dimensional case and agrees very well with the one found by the wave-function approach in the two-particle-hole subspace. In three-dimensional Fermi-polaron systems with mass imbalance of impurity and bath atoms, polaron energy and quasiparticle residue can be accurately determined over a broad range of impurity masses. Furthermore, the spectral function of an imbalanced polaron demonstrates the stability of the quasiparticle and also allows us to locate the repulsive polaron as an excited state. The quantitative exactness of two-particle-hole wave functions is investigated, resulting in a relative lowering of polaronic energies in the mass-imbalance phase diagram. Tan's contact coefficient for the mass-balanced polaron system is found to be in good agreement with variational methods. Mass-imbalanced systems can be studied experimentally by ultracold atom mixtures such as {sup 6}Li-{sup 40}K. In the second part of the thesis, the ground state of a two-dimensional system of Bose particles of spin zero, interacting via a repulsive Gaussian-Core potential, is investigated by means of path integral Monte Carlo simulations. The quantum phase diagram is qualitatively identical to that of two-dimensional Yukawa
Noble gases in meteorites and terrestrial planets
Wacker, J. F.
Terrestrial planets and chondrites have noble gas platforms that are sufficiently alike, especially Ne/Ar, that they may have acquired their noble gases by similar processes. Meteorites presumably obtained their noble gases during formation in the solar nebula. Adsorption onto C - the major gas carrier in chondrites - is the likely mechanism for trapping noble gases; recent laboratory simulations support this hypothesis. The story is more complex for planets. An attractive possibility is that the planets acquired their noble gases in a late accreting veneer of chondritic material. In chondrites, noble gases correlate with C, N, H, and volatile metals; by Occam's Razor, we would expect a similar coupling in planets. Indeed, the Earth's crust and mantle contain chondritic like trace volatiles and PL group metals, respectively and the Earth's oceans resemble C chondrites in their enrichment of D (8X vs 8-10X of the galactic D/H ratio). Models have been proposed to explain some of the specific noble gas patterns in planets. These include: (1) noble gases may have been directly trapped by preplanetary material instead of arriving in a veneer; (2) for Venus, irradiation of preplanetary material, followed by diffusive loss of Ne, could explain the high concentration of AR-36; (3) the Earth and Venus may have initially had similar abundances of noble gases, but the Earth lost its share during the Moon forming event; (4) noble gases could have been captured by planetestimals, possibly leading to gravitational fractionation, particularly of Xe isotopes and (5) noble gases may have been dissolved in the hot outer portion of the Earth during contact with a primordial atmosphere.
FERMI@Elettra FEL Design Technical Optimization Final Report
Energy Technology Data Exchange (ETDEWEB)
Fawley, William; Penn, Gregory; Allaria, Enrico; De Ninno,Giovanni; Graves, William
This is the final report of the FEL Design Group for the Technical Optimization Study for the FERMI{at}ELETTRA project. The FERMI{at}ELETTRA project is based on the principle of harmonic upshifting of an initial ''seed'' signal in a single pass, FEL amplifier employing multiple undulators. There are a number of FEL physics principles which underlie this approach to obtaining short wavelength output: (1) the energy modulation of the electron beam via the resonant interaction with an external laser seed (2) the use of a chromatic dispersive section to then develop a strong density modulation with large harmonic overtones (3) the production of coherent radiation by the microbunched beam in a downstream radiator. Within the context of the FERMI project, we discuss each of these elements in turn.
Breakdown of the Fermi Liquid Description for Strongly Interacting Fermions
Sagi, Yoav; Drake, Tara E.; Paudel, Rabin; Chapurin, Roman; Jin, Deborah S.
The nature of the normal state of an ultracold Fermi gas in the BCS-BEC crossover regime is an intriguing and controversial topic. While the many-body ground state remains a condensate of paired fermions, the normal state must evolve from a Fermi liquid to a Bose gas of molecules as a function of the interaction strength. How this occurs is still largely unknown. We explore this question with measurements of the distribution of single-particle energies and momenta in a nearly homogeneous gas above Tc . The data fit well to a function that includes a narrow, positively dispersing peak that corresponds to quasiparticles and an "incoherent background" that can accommodate broad, asymmetric line shapes. We find that the quasiparticle's spectral weight vanishes abruptly as the strength of interactions is modified, which signals the breakdown of a Fermi liquid description. Such a sharp feature is surprising in a crossover.
Emission versus Fermi coordinates: applications to relativistic positioning systems
Energy Technology Data Exchange (ETDEWEB)
Bini, D [Istituto per le Applicazioni del Calcolo ' M. Picone' , CNR I-00161 Rome (Italy); Geralico, A [ICRA, University of Rome ' La Sapienza' , I-00185 Rome (Italy); Ruggiero, M L; Tartaglia, A [Dipartimento di Fisica, Politecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino (Italy)
A four-dimensional relativistic positioning system for a general spacetime is constructed by using the so-called emission coordinates. The results apply in a small region around the world line of an accelerated observer carrying a Fermi triad, as described by the Fermi metric. In the case of a Schwarzschild spacetime modeling the gravitational field around the Earth and an observer at rest at a fixed spacetime point, these coordinates realize a relativistic positioning system alternative to the current GPS system. The latter is indeed essentially conceived as Newtonian, so that it necessarily needs taking into account at least the most important relativistic effects through post-Newtonian corrections to work properly. Previous results concerning emission coordinates in flat spacetime are thus extended to this more general situation. Furthermore, the mapping between spacetime coordinates and emission coordinates is completely determined by means of the world function, which in the case of a Fermi metric can be explicitly obtained.
Broad band spectral energy distribution studies of Fermi bright blazars
Energy Technology Data Exchange (ETDEWEB)
Monte, C., E-mail: firstname.lastname@example.com [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Dipartimento di Fisica ' M. Merlin' dell' Universita e del Politecnico, I-70126 Bari (Italy); Giommi, P.; Cavazzuti, E.; Gasparrini, D. [Agenzia Spaziale Italiana (ASI) Science Data Center I-00044 Frascati (Roma) (Italy); Raino, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Dipartimento di Fisica ' M. Merlin' dell' Universita e del Politecnico, I-70126 Bari (Italy); Fuhrmann, L.; Angelakis, E. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Villata, M.; Raiteri, C.M. [INAF, Osservatorio Astronomico di Torino, I-10025 Pino Torinese (Italy); Perri, M. [Agenzia Spaziale Italiana (ASI) Science Data Center I-00044 Frascati (Roma) (Italy); Richards, J. [California Institute of Technology, Pasadena, CA (United States)
The Fermi Gamma-ray Space Telescope was successfully launched on June 11, 2008 and has already opened a new era for gamma-ray astronomy. The Large Area Telescope (LAT), the main instrument on board Fermi, presents a significant improvement in sensitivity over its predecessor EGRET, due to its large field of view and effective area, combined with its excellent timing capabilities. The preliminary results of the Spectral Energy Distribution Analysis performed on a sample of bright blazars are presented. For this study, the data from the first three months of data collection of Fermi have been used. The analysis is extended down to radio, mm, near-IR, optical, UV and X-ray bands and up to TeV energies based on unprecedented sample of simultaneous multi-wavelength observations by GASP-WEBT.
Broad band spectral energy distribution studies of Fermi bright blazars
Monte, C.; Giommi, P.; Cavazzuti, E.; Gasparrini, D.; Rainò, S.; Fuhrmann, L.; Angelakis, E.; Villata, M.; Raiteri, C. M.; Perri, M.; Richards, J.
The Fermi Gamma-ray Space Telescope was successfully launched on June 11, 2008 and has already opened a new era for gamma-ray astronomy. The Large Area Telescope (LAT), the main instrument on board Fermi, presents a significant improvement in sensitivity over its predecessor EGRET, due to its large field of view and effective area, combined with its excellent timing capabilities. The preliminary results of the Spectral Energy Distribution Analysis performed on a sample of bright blazars are presented. For this study, the data from the first three months of data collection of Fermi have been used. The analysis is extended down to radio, mm, near-IR, optical, UV and X-ray bands and up to TeV energies based on unprecedented sample of simultaneous multi-wavelength observations by GASP-WEBT.
Constrain the SED Type of Unidentified Fermi Objects
Directory of Open Access Journals (Sweden)
An-Li Tsai
Full Text Available 2FGL J1823.8+4312 and 2FGL J1304.1-2415 are two unidentified Fermi objects which are associated with cluster of galaxies. In order to exam the possibility of cluster of galaxies as gamma-ray emitters, we search for counterpart of these two unidentified Fermi objects in other wavebands. However, we find other candidate to be more likely the counterpart of the unidentified Fermi object for both sources. We compare their light curves and SEDs in order to identify their source types. However, data at millimeter and sub-millimeter wavebands, which is important for us to constrain the SED at synchrotron peak, is lacking of measurement. Therefore, we proposed to SMA observation for these two sources. We have got data and are doing further analysis.
Fermi-LAT Observations toward the Galactic Center
Murgia, Simona
The inner region of the Milky Way is one of the most interesting and complex regions of the γ-ray sky. Intense interstellar emission and point sources contribute to it, as well as other potential components such as an unresolved population of point sources and dark matter. In recent years, claims have been made of an excess consistent with a dark matter annihilation signal in the data collected with the Fermi Large Area Telescope (Fermi-LAT). Although these results are intriguing, the complexity involved in modeling the foreground and background emission from conventional astrophysical sources of γ-rays makes a conclusive interpretation of these results challenging. In these proceedings, I discuss Fermi-LAT observations of the Galactic center region, the methodology for point source detection and treatment of the interstellar emission, the characterization of the GeV excess, and implications for dark matter.
Harper Operator, Fermi Curves and Picard-Fuchs Equation
Li, Dan
This paper is a continuation of the work on the spectral problem of the Harper operator using algebraic geometry. We continue to discuss the local monodromy of algebraic Fermi curves based on Picard-Lefschetz formula. The density of states over approximating components of Fermi curves satisfies a Picard-Fuchs equation. By the property of Landen transformation, the density of states has a Lambert series as the quarter period. A q-expansion of the energy is derived from a mirror map as in the B-model.
String theory, quantum phase transitions, and the emergent Fermi liquid.
Cubrović, Mihailo; Zaanen, Jan; Schalm, Koenraad
A central problem in quantum condensed matter physics is the critical theory governing the zero-temperature quantum phase transition between strongly renormalized Fermi liquids as found in heavy fermion intermetallics and possibly in high-critical temperature superconductors. We found that the mathematics of string theory is capable of describing such fermionic quantum critical states. Using the anti-de Sitter/conformal field theory correspondence to relate fermionic quantum critical fields to a gravitational problem, we computed the spectral functions of fermions in the field theory. By increasing the fermion density away from the relativistic quantum critical point, a state emerges with all the features of the Fermi liquid.
Generalized Jastrow variational method for dense Fermi systems
Inguva, Ramarao; Smith, C. Ray
In this paper, we outline a simple method whereby the antisymmetry of the wave function can be incorporated exactly in the Jastrow many-body theory. Applications of this method to the "homework problem" for neutron matter using the hypernetted-chain approximation give results in very good agreement with the Fermi-hypernetted chain approximation calculations of Fantoni and Rosati. The calculations for liquid3He at a Fermi wave number k F=0.75 Å-1 give results close to the Monte Carlo calculations of Ceperley, Chester, and Kalos.
Detecting Superlight Dark Matter with Fermi-Degenerate Materials
Hochberg, Yonit; Pyle, Matt; Zhao, Yue; Zurek, Kathryn M.
We examine in greater detail the recent proposal of using superconductors for detecting dark matter as light as the warm dark matter limit of O $$ \\mathcal{O} $$ (keV). Detection of suc light dark matter is possible if the entire kinetic energy of the dark matter is extracted in the scattering, and if the experiment is sensitive to O $$ \\mathcal{O} $$ (meV) energy depositions. This is the case for Fermi-degenerate materials in which the Fermi velocity exceeds the dark matter velocity dispersi...
Fermi Bubbles: an elephant in the gamma-ray sky
Directory of Open Access Journals (Sweden)
Malyshev Dmitry
Full Text Available The Fermi bubbles are one of the most remarkable features in the gamma-ray sky revealed by the Fermi Large Area Telescope (LAT. The nature of the gamma-ray emission and the origin of the bubbles are still open questions. In this note, we will review some basic features of leptonic and hadronic modes of gamma-ray production. At the moment, gamma rays are our best method to study the bubbles, but in order to resolve the origin of the bubbles multi-wavelength and multi-messenger observations will be crucial.
Electronic structure, Fermi surface and optical properties of metallic compound Be{sub 8}(B{sub 48})B{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Reshak, A.H. [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Azam, Sikander, E-mail: email@example.com [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); Alahmed, Z.A. [Department of Physics and Astronomy, King Saud University, Riyadh 11451 (Saudi Arabia); Chyský, Jan [Department of Instrumentation and Control Engineering, Faculty of Mechanical Engineering, CTU in Prague, Technicka 4, 166 07 Prague 6 (Czech Republic)
The band structure, density of states, electronic charge density, Fermi surface and optical properties for B{sub 8}(Be{sub 48})B{sub 2} compound has been investigated in the support of density functional theory (DFT). The atomic positions of B{sub 8}(Be{sub 48})B{sub 2} compound were optimized by minimization of the forces acting on the atoms using the full potential linear augmented plane wave (FPLAPW) method. We have employed the local density approximation (LDA), generalized gradient approximation (GGA) and Engal-Vosko GGA (EVGGA) to indulgence the exchange correlation potential by solving Kohn–Sham equations. The result shows that the compound is metallic with sturdy hybridization near the Fermi energy level (E{sub F}). The density of states at Fermi energy, N(E{sub F}), is determined by the overlaping between B-p, B-s and Be-s states. This overlaping is strong enough indicating metallic origin with different values of N(E{sub F}). These values are 16.4, 16.27 and 14.89 states/eV, and the corresponding bare linear low-temperature electronic specific heat coefficient (γ) is found to be 2.84, 2.82 and 2.58 mJ/mol K{sup 2} for EVGGA, GGA and LDA respectively. There exists a strong hybridization between B-s and B-p states, also between B-s and Be-p states around the Fermi level. The Fermi surface is composed of three sheets. These sheets consist of set of holes and electrons. The bonding features of the compounds are analyzed using the electronic charge density in the (101 and −101) crystallographic planes and also the analyzing of charge density shows covalent bonding between B and B. The linear optical properties are also deliberated and discussed in particulars. - Highlights: • The compound is metallic. • The density of states at the Fermi energy is calculated. • The bare linear low-temperature electronic specific heat coefficient is obtained. • Fermi surface is composed of three sheets. • The bonding features are analyzed using the electronic
Photon transport of the superradiant TeraFERMI THz beamline at the FERMI free-electron laser.
Svetina, Cristian; Mahne, Nicola; Raimondi, Lorenzo; Perucchi, Andrea; Di Pietro, Paola; Lupi, Stefano; Schmidt, Bernhard; Zangrando, Marco
TeraFERMI is the new terahertz (THz) beamline for pump-probe studies on the femtosecond time-scale, under construction at the FERMI free-electron laser (FEL) facility in Trieste, Italy. The beamline will take advantage of the coherent radiation emitted by the spent electrons from the FEL undulators, before being dumped. This will result in short, coherent, high-power THz pulses to be used as a pump beam, in order to modulate structural properties of matter, thereby inducing phase transitions. The TeraFERMI beamline collects THz radiation in the undulator hall and guides it along a beam pipe which is approximately 30 m long, extending across the safety hutch and two shielding walls. Here the optical design, which will allow the efficient transport of the emitted THz radiation in the experimental hall, is presented.
Fermi Solar Flare X-Ray and Gamma-Ray Observations
National Aeronautics and Space Administration — The Fermi Gamma-ray Space Telescope was launched in June 2008 to explore high-energy phenomena in the Universe. This GI program is targeted specifically at Fermi...
Non-Fermi liquid fixed points of a two-channel Anderson model
Energy Technology Data Exchange (ETDEWEB)
Ferreira, J.V.B.; Oliveira, L.N. de; Cox, D.L.; Libero, V.L. E-mail: email@example.com
A generalized two-channel Anderson Hamiltonian is diagonalized via the numerical renormalization group. The spectrum shows non-Fermi liquid fixed point for isotropic channel hybridization and normal Fermi liquid for the anisotropic case.
Search for a neutrino emission from the Fermi Bubbles with the ANTARES telescope
The first search for neutrinos from the Fermi Bubbles is presented using data collected by the ANTARES telescope. No evidence of a neutrino signal from the Fermi Bubbles region was found, hence upper limits were calculated for different energy cutoffs.
Voluntary reporting of greenhouse gases, 1995
Energy Technology Data Exchange (ETDEWEB)
The Voluntary Reporting Program for greenhouse gases is part of an attempt by the U.S. Government to develop innovative, low-cost, and nonregulatory approaches to limit emissions of greenhouse gases. It is one element in an array of such programs introduced in recent years as part of the effort being made by the United States to comply with its national commitment to stabilize emissions of greenhouse gases under the Framework Convention on Climate Change. The Voluntary Reporting Program, developed pursuant to Section 1605(b) of the Energy Policy Act of 1992, permits corporations, government agencies, households, and voluntary organizations to report to the Energy Information Administration (EIA) on actions taken that have reduced or avoided emissions of greenhouse gases.
Roadside management strategies to reduce greenhouse gases.
Californias Global Warming Solutions Act of 2006 (AB 32), Sustainable Communities and Climate Protection Act : (SB 375), and Executive Order S-14-08 direct Caltrans to develop actions to reduce greenhouse gases (GHGs). Air : pollution reduction is...
Mean-field energy-level shifts and dielectric properties of strongly polarized Rydberg gases
Zhelyazkova, V; Hogan, S D
Mean-field energy-level shifts arising as a result of strong electrostatic dipole interactions within dilute gases of polarized helium Rydberg atoms have been probed by microwave spectroscopy. The Rydberg states studied had principal quantum numbers $n=70$ and 72, and electric dipole moments of up to 14050 D, and were prepared in pulsed supersonic beams at particle number densities on the order of $10^{8}$ cm$^{-3}$. Comparisons of the experimental data with the results of Monte Carlo calculations highlight effects of the distribution of nearest-neighbor spacings in the pulsed supersonic beams, and the dielectric properties of the strongly polarized Rydberg gases, on the microwave spectra. These observations reflect the emergence of macroscopic electrical properties of the atomic samples when strongly polarized.
The adsorption sites of rare gases on metallic surfaces: a review
Diehl, R. D.; Seyller, Th; Caragiu, M.; Leatherman, G. S.; Ferralis, N.; Pussi, K.; Kaukasoina, P.; Lindroos, M.
During the past six years, the adsorption geometries of several rare gases in structures having several different symmetries on a variety of substrates were determined using low-energy electron diffraction (LEED). In most of these studies, a preference is found for the rare gas atoms to adsorb in the low-coordination sites. Only in the case of adsorption on graphite has a clear preference for a high-coordination site for a rare gas atom been found. This unexpected behaviour is not yet completely understood, although recent density functional theory (DFT) calculations for these and similar surfaces suggest that this is a general phenomenon. This paper reviews the early studies that were presages of the discovery of top site adsorption for rare gases, the discovery itself, and the present state of understanding of this curiosity. It also details some of the features of the LEED experiments and analysis that are specific to the case of rare gas adsorption.
Comparing models for the ground state energy of a trapped one-dimensional Fermi gas with a single impurity
Loft, N. J. S.; Kristensen, L. B.; Thomsen, A. E.; Zinner, N. T.
We discuss the local density approximation approach to calculating the ground state energy of a one-dimensional Fermi gas containing a single impurity, and compare the results with exact numerical values that we have for up to 11 particles for general interaction strengths and up to 30 particles in the strongly interacting case. We also calculate the contact coefficient in the strongly interacting regime. The different theoretical predictions are compared to recent experimental results with few-atom systems. Firstly, we find that the local density approximation suffers from great ambiguity in the few-atom regime, yet it works surprisingly well for some models. Secondly, we find that the strong interaction theories quickly break down when the number of particles increase or the interaction strength decreases.
Biological production of products from waste gases
Gaddy, James L.
A method and apparatus are designed for converting waste gases from industrial processes such as oil refining, and carbon black, coke, ammonia, and methanol production, into useful products. The method includes introducing the waste gases into a bioreactor where they are fermented to various products, such as organic acids, alcohols, hydrogen, single cell protein, and salts of organic acids by anaerobic bacteria within the bioreactor. These valuable end products are then recovered, separated and purified.
Hydrodynamic limits of kinetic equations for polyatomic and reactive gases
Directory of Open Access Journals (Sweden)
Bisi M.
Full Text Available Starting from a kinetic BGK-model for a rarefied polyatomic gas, based on a molecular structure of discrete internal energy levels, an asymptotic Chapman-Enskog procedure is developed in the asymptotic continuum limit in order to derive consistent fluid-dynamic equations for macroscopic fields at Navier-Stokes level. In this way, the model allows to treat the gas as a mixture of mono-atomic species. Explicit expressions are given not only for dynamical pressure, but also for shear stress, diffusion velocities, and heat flux. The analysis is shown to deal properly also with a mixture of reactive gases, endowed for simplicity with translational degrees of freedom only, in which frame analogous results can be achieved.
Willden, Jeff
"Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…
Delayed Higher-Order Optical Nonlinearities in Noble Gases
Tarazkar, Maryam; Romanov, Dmitri; Levis, Robert
The role of higher-order Kerr effect (HOKE) in femtosecond laser filamentation is currently at the center of a controversy, as alleged crossover from positive to negative nonlinear refractive index at higher intensities was proposed to cause filament stabilization. Experimental evidence of HOKE crossover or lack thereof is being hotly debated. Motivated by this debate, we report the frequency-dependent nonlinear refractive index coefficients n2 and n4 for a series of atmospheric-pressure noble gases: helium, neon, argon, krypton, and xenon. The corresponding atomic hyperpolarizability coefficients are obtained via auxiliary static electric field approach developed on the basis of ab initio calculations implemented in Dalton program and performed at the CCSD level of theory with t-Aug-cc-PV5Z basis set. The n4 index is obtained using the relations between the degenerate six-wave mixing coefficient and some other frequency-dependent second hyperpolarizability coefficients, which can be calculated on the basis of n2via the auxiliary field approach. For all the investigated gases, the n4 indices are found to be positive over the wavelength range 300 nm-1500 nm. This result runs counter to the HOKE crossover hypothesis. The calculated n4 indices demonstrate considerable temporal dispersion, which progressively increases from helium to xenon. This feature implies delayed nonlinearity and calls for modifications in current theoretical models of filamentation process. We gratefully acknowledge financial support through AFOSR MURI Grant No. FA9550-10-1-0561.
Asymptotics for Two-dimensional Atoms
DEFF Research Database (Denmark)
Nam, Phan Thanh; Portmann, Fabian; Solovej, Jan Philip
We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E^{\\TF}(\\lambd......We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E......^{\\TF}(\\lambda)$ is given by a Thomas-Fermi type variational problem and $c^{\\rm H}\\approx -2.2339$ is an explicit constant. We also show that the radius of a two-dimensional neutral atom is unbounded when $Z\\to \\infty$, which is contrary to the expected behavior of three-dimensional atoms....
Source gases: Concentrations, emissions, and trends
Fraser, Paul J.; Harriss, Robert; Penkett, Stuart A.; Makide, Yoshihiro; Sanhueza, Eugenio; Alyea, Fred N.; Rowland, F. Sherwood; Blake, Don; Sasaki, Toru; Cunnold, Derek M.
Source gases are defined as those gases that influence levels of stratospheric ozone (O3) by transporting species containing halogen, hydrogen, and nitrogen to the stratosphere. Examples are the CFC's, methane (CH4), and nitrous oxide (N2O). Other source gases that also come under consideration in an atmospheric O3 context are those that are involved in the O3 or hydroxyl (OH) radical chemistry of the troposphere. Examples are CH4, carbon monoxide (CO), and nonmethane hydrocarbons (NMHC's). Most of the source gases, along with carbon dioxide (CO2) and water vapor (H2O), are climatically significant and thus affect stratospheric O3 levels by their influence on stratospheric temperatures. Carbonyl sulphide (COS) could affect stratospheric O3 through maintenance of the stratospheric sulphate aerosol layer, which may be involved in heterogeneous chlorine-catalyzed O3 destruction. The previous reviews of trends and emissions of source gases, either from the context of their influence on atmospheric O3 or global climate change, are updated. The current global abundances and concentration trends of the trace gases are given in tabular format.
A search for neutrino emission from the Fermi bubbles with the ANTARES telescope
Adrián-Martínez, S.; Albert, A.; Al Samarai, I.; André, M.; Anton, G.; Anvar, S.; Ardid, M.; Astraatmadja, T.; Aubert, J. J.; Baret, B.; Barrios-Martí, J.; Basa, S.; Bertin, V.; Biagi, S.; Bigongiari, C.; Bogazzi, C.; Bouhou, B.; Bouwhuis, M. C.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Cârloganu, C.; Carr, J.; Cecchini, S.; Charif, Z.; Charvis, Ph; Chiarusi, T.; Circella, M.; Classen, F.; Coniglione, R.; Core, L.; Costantini, H.; Coyle, P.; Creusot, A.; Curtil, C.; De Bonis, G.; Dekeyser, I.; Deschamps, A.; Donzaud, C.; Dornic, D.; Dorosti, Q.; Drouhin, D.; Dumas, A.; Eberl, T.; Emanuele, U.; Enzenhöfer, A.; Ernenwein, J. P.; Escoffier, S.; Fehn, K.; Fermani, P.; Flaminio, V.; Folger, F.; Fritsch, U.; Fusco, L. A.; Galatà, S.; Gay, P.; Geißelsöder, S.; Geyer, K.; Giacomelli, G.; Giordano, V.; Gleixner, A.; Gómez-González, J. P.; Graf, K.; Guillard, G.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Herold, B.; Hößl, J.; Hugon, C.; James, C. W.; de Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U.; Kooijman, P.; Kouchner, A.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lambard, E.; Lambard, G.; Larosa, G.; Lattuada, D.; Lefèvre, D.; Leonora, E.; Lo Presti, D.; Loehner, H.; Loucatos, S.; Louis, F.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martínez-Mora, J. A.; Martini, S.; Michael, T.; Montaruli, T.; Morganti, M.; Müller, C.; Neff, M.; Nezri, E.; Palioselitis, D.; Pǎvǎlaş, G. E.; Perrina, C.; Popa, V.; Pradier, T.; Racca, C.; Riccobene, G.; Richter, R.; Rivière, C.; Robert, A.; Roensch, K.; Rostovtsev, A.; Samtleben, D. F E; Sanguineti, M.; Sapienza, P.; Schmid, J.; Schnabel, J.; Schulte, S.; Schüssler, F.; Seitz, T.; Shanidze, R.; Sieger, C.; Simeone, F.; Spies, A.; Spurio, M.; Steijger, J. J M; Stolarczyk, Th; Sánchez-Losa, A.; Taiuti, M.; Tamburini, C.; Tayalati, Y.; Trovato, A.; Vallage, B.; Vallée, C.; Van Elewyck, V.; Vecchi, M.; Vernin, P.; Visser, E.; Wagner, S.; Wilms, J.; de Wolf, E.; Yatkin, K.; Yepes, H.; Zornoza, J. D.; Zúñiga, J.
Analysis of the Fermi-LAT data has revealed two extended structures above and below the Galactic Centre emitting gamma rays with a hard spectrum, the so-called Fermi bubbles. Hadronic models attempting to explain the origin of the Fermi bubbles predict the emission of high-energy neutrinos and gamma
Band Structure and Fermi Surface of Cu2Sb by the LMTO Method
DEFF Research Database (Denmark)
Jan, J. P.; Skriver, Hans Lomholt
The linear muffin-tin orbital (LMTO) method of bandstructure calculation has been applied to the simple tetragonal compound Cu2Sb. The d bands of Cu lie substantially below the Fermi level, and the Fermi surface is a recognizable distortion of the free-electron model. The Fermi surface has sheets...
An Atomistic Study of the Incorporation and Diffusion of Noble Gases in Silicate Minerals
Pinilla, C.; Valencia, K.; Martinez-Mendoza, C.; Allan, N.
Trace elements are widely used to unravel magmatic processes and constrain the chemical differentiation of the Earth. Central to this enterprise is understanding the controls on trace element fractionation between solid and liquid phases and thus the energetics of incorporating trace elements into crystals. In this contribution we focus on the incorporation of noble gases into crystals, with implications for the degassing processes in the Earth and the atmosphere. We use both ab-initio and classical calculations using interatomic potentials to study the uptake of the noble gases He, Ne and Ar into solid silicates. We calculate atomic defect energies of incorporation both at vacancies and at interstitial positions in solid forsterite. We use these energies to estimate the total uptake of the noble gases bulk into the crystal as a function of temperature. Such concentrations are found to be very low (10-3 and 10-10 ppm) for He up to Ar respectively with the noble gases incorporated predicted to be more favorable at intrinsic vacancies of Si or Mg or at interstitials sites. We also look at the diffusion of these minerals within the lattice and estimate activation energies for such processes. Our results support the hypothesis that noble gases have very low solubilities in bulk solid minerals. Other mechanisms such as adsorption at internal and external interfaces, voids and grain boundaries that can play a mayor role in their storage are also briefly discussed.
Chemical potential and internal energy of the noninteracting Fermi ...
Indian Academy of Sciences (India)
... it increases above the Fermi energy for dimensions below 2 as a result of high entropy. The ranges of validity of the truncated series expansions of these quantities are extended from low to intermediate temperature regime as well as from high to relatively low density regime by using the Pad ́e approximant technique.
Current correlation functions of ideal Fermi gas at finite temperature
Indian Academy of Sciences (India)
Ca; 71.45.Gm. 1. Introduction. The transverse and longitudinal current–current correlation functions describing the cur- rent fluctuations induced in the electron system by a weak external probe perpendicular and parallel to the propagation of electron wave, respectively, are two basic quantities in the theory of Fermi liquid.
Diboson Signals via Fermi Scale Spin-One States
DEFF Research Database (Denmark)
Franzosi, Diogo Buarque; Frandsen, Mads T.; Sannino, Francesco
ATLAS and CMS observe deviations from the expected background in diboson invariant mass searches of new resonances around 2 TeV. We provide a general analysis of the results in terms of spin-one resonances and find that Fermi scale composite dynamics can be the culprit. The analysis and methodology...
Finite Fermi systems theory and self-consistency relations
Energy Technology Data Exchange (ETDEWEB)
Khodel, V.A.; Saperstein, E.E. (Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Moscow. Inst. Atomnoj Ehnergii)
The self-consistent theory of the finite Fermi systems is outlined. This approach is based on the same Fermi liquid theory principles as the familiar theory for finite Fermi systems (FFS) by Migdal. We show that the basic Fermi system properties can be evaluated in terms of the quasiparticle Lagrangian Lsub(q) which incorporates the energy dependency effects. This Lagrangian is defined so that the corresponding Lagrange equations should coincide with the FFS theory equations of motion of the quasiparticles. The quasiparticle energy Esub(q) defined in the terms of the quasiparticle Lagrangian Lsub(q) according to the usual canonical rules is shown to be equal to the binding energy E/sub 0/ of the system. For a given Lagrangian Lsub(q) the particle densities in nuclei, the nuclear single-particle spectra, the low-lying collective states (LCS) properties, and the amplitude of the interquasiparticle interaction are also evaluated. The suggested approach is compared with the Hartree-Fock theory with effective forces.
Three scientists to receive presidential Enrico Fermi award
"Secretary of Energy Spencer Abraham today named John Bahcall, Raymond Davis, Jr. and Seymour Sack as winners of the Enrico Fermi Award. ... Drs. Bahcall and Davis will receive the award for their research in neutrino physics. Dr. Sack will receive the award for his contributions to national security" (1 page).
Moon and quiet Sun detection with Fermi-LAT observatory
Energy Technology Data Exchange (ETDEWEB)
Brigida, M., E-mail: email@example.com [Dipartimento Interateneo di Fisica ' Michelangelo Merlin' , dell' Universita degli Studi e del Politecnico di Bari and INFN Sezione di Bari, Via Amendola 173, I-70126 Bari (Italy)
The Fermi gamma-ray space telescope is an international mission supporting two science instruments, the Gamma-Ray Burst Monitor (GBM), covering the energy range from few keV to 30 MeV, and the Large Area Telescope (LAT), a pair-conversion detector operating at energies from 30 MeV to 300 GeV. The Fermi telescope was successfully launched on June 11, 2008 and has been surveying the sky in gamma rays since August 2008. During the first months of the mission, Fermi has detected high-energy gamma rays from the Moon and quiet Sun since the first weeks of data taking. This emission is produced by interactions of cosmic rays; by nucleons with the solar and lunar surface (albedo), and electrons with solar photons in the heliosphere. The heliospheric emission is produced by inverse-Compton scattering and is predicted to be extended. Both Moon and the quiet Sun was detecte d by EGRET on CGRO with low statistics, but Fermi is the only gamma-ray mission capable of detecting the Moon and the quiet Sun and monitoring it over the full 24th solar cycle. Here we present the analysis relative to the first months including the observation of the Moon and the Sun, the spectral analysis, the fluxes measurements and finally a comparison with models and previous detections.
Multi-Band Spectral Properties of Fermi Blazars
Indian Academy of Sciences (India)
Galaxies: active; BL Lacertae objects; general; gamma rays; observations. Abstract. The multi-band data covering optical, X-ray and -ray energy regions of 130 Fermi blazars in the First LAT AGN Catalog (1LAC) were collected to investigate the broadband spectral properties. The composite spectral indices show that ...
The First Fermi-LAT Gamma-Ray Burst Catalog
Ackermann, M.; et al., [Unknown; van der Horst, A.J.
In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (gsim 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected
Constraining decaying dark matter with Fermi LAT gamma-rays
Energy Technology Data Exchange (ETDEWEB)
Zhang, Le; Sigl, Guenter [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Weniger, Christoph; Maccione, Luca [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Redondo, Javier [Max-Planck-Institut fuer Physik, Muenchen (Germany)
High energy electrons and positrons from decaying dark matter can produce a significant flux of gamma rays by inverse Compton off low energy photons in the interstellar radiation field. This possibility is inevitably related with the dark matter interpretation of the observed PAMELA and FERMI excesses. The aim of this paper is providing a simple and universal method to constraint dark matter models which produce electrons and positrons in their decay by using the Fermi LAT gamma-ray observations in the energy range between 0.5 GeV and 300 GeV. We provide a set of universal response functions that, once convolved with a specific dark matter model produce the desired constraint. Our response functions contain all the astrophysical inputs such as the electron propagation in the galaxy, the dark matter profile, the gamma-ray fluxes of known origin, and the Fermi LAT data. We study the uncertainties in the determination of the response functions and apply them to place constraints on some specific dark matter decay models that can well fit the positron and electron fluxes observed by PAMELA and Fermi LAT. To this end we also take into account prompt radiation from the dark matter decay. We find that with the available data decaying dark matter cannot be excluded as source of the PAMELA positron excess. (orig.)
Animating Fermi - A Collaboration Between Art Students and Astronomers
Arcadias, Laurence
Undergraduate animation students at the Maryland Institute College of Art teamed up with scientists from the Fermi Gamma-ray Space Telescope to produce a set of animations on several astronomy topics. We describe the process and discuss the results, including educational benefits and the cross-cultural experience. These animations are freely available online.
Multi-Band Spectral Properties of Fermi Blazars Benzhong Dai ...
Indian Academy of Sciences (India)
Galaxies: active—BL Lacertae objects—general—gamma rays—observations. 1. Introduction. The First Fermi-LAT Catalogue (1LAC) of AGN, corresponding to 11 months of data collected in scientific operation mode, includes 709 AGNs, comprising 300 BL. Lacs, 296 FSRQs, 41 AGNs of other types and 72 AGNs of ...
All-Sky Monitoring of Variable Sources with Fermi GBM
Wilson-Hodge, Colleen A.; Cherry, Michael L.; Case, Gary L.; Camero-Arranz, Ascension; Chaplin, Vandiver; Connaughton, Valerie; Finger, Mark H.; Jenke, Pater; Rodi, James C.; Baumgartner, Wayne H.;
This slide presentation reviews the monitoring of variable sources with the Fermi Gamma Ray Burst Monitor (GBM). It reviews the use of the Earth Occultation technique, the observations of the Crab Nebula with the GBM, and the comparison with other satellite's observations. The instruments on board the four satellites indicate a decline in the Crab from 2008-2010.
Fermi liquid of two-dimensional polar molecules
Lu, Z.K; Shlyapnikov, G.V.
We study Fermi-liquid properties of a weakly interacting two-dimensional gas of single-component fermionic polar molecules with dipole moments d oriented perpendicularly to the plane of their translational motion. This geometry allows the minimization of inelastic losses due to chemical reactions
External meeting - Geneva University: A lab in a trap: quantum gases in optical lattices
GENEVA UNIVERSITY ECOLE DE PHYSIQUE Département de physique nucléaire et corspusculaire 24, Quai Ernest-Ansermet 1211 GENEVE 4 - Tél: 022 379 62 73 - Fax: 022 379 69 92 Monday 16 April 2007 PARTICLE PHYSICS SEMINAR at 17:00 - Stückelberg Auditorium A lab in a trap: quantum gases in optical lattices by Prof. Tilman Esslinger / Department of Physics, ETH Zurich The field of ultra cold quantum gases has seen an astonishing development during the last ten years. With the demonstration of Bose-Einstein condensation in weakly interacting atomic gases a theoretical concept of unique beauty could be witnessed experimentally. Very recent developments have now made it possible to engineer atomic many-body systems which are dominated by strong interactions. A major driving force for these advances are experiments in which ultracold atoms are trapped in optical lattices. These systems provide anew avenue for designing and studying quantum many-body systems. Exposed to the crystal structure of interfering laser wave...
Energy Technology Data Exchange (ETDEWEB)
Lim, Suh Yeon
This book is written to teach atom structure in very easy way. It is divided into nine chapters, which indicates what is the components of matter? when we divide matter continuously, it becomes atom, what did atom look like? particles comprised of matter is not only atom, discover of particles comprised of atom, symbol of element, various radiation, form alchemy to nuclear transmutation, shape of atom is evolving. It also has various pictures in each chapters to explain easily.
Saedi, Amirmehdi; van Houselt, Arie; van Gastel, Raoul; Poelsema, Bene; Zandvliet, Harold J W
We demonstrate the feasibility of controlling an atomic scale mechanical device by an external electrical signal. On a germanium substrate, a switching motion of pairs of atoms is induced by electrons that are directly injected into the atoms with a scanning tunneling microscope tip. By precisely controlling the tip current and distance we make two atom pairs behave like the flippers of an atomic-sized pinball machine. This atomic scale mechanical device exhibits six different configurations.
Flavor Gauge Models Below the Fermi Scale
Energy Technology Data Exchange (ETDEWEB)
Babu, K. S. [Oklahoma State U.; Friedland, A. [SLAC; Machado, P. A.N. [Madrid, IFT; Mocioiu, I. [Penn State U.
The mass and weak interaction eigenstates for the quarks of the third generation are very well aligned, an empirical fact for which the Standard Model offers no explanation. We explore the possibility that this alignment is due to an additional gauge symmetry in the third generation. Specifically, we construct and analyze an explicit, renormalizable model with a gauge boson, $X$, corresponding to the $B-L$ symmetry of the third family. Having a relatively light (in the MeV to multi-GeV range), flavor-nonuniversal gauge boson results in a variety of constraints from different sources. By systematically analyzing 20 different constraints, we identify the most sensitive probes: kaon, $D^+$ and Upsilon decays, $D-\\bar{D}^0$ mixing, atomic parity violation, and neutrino scattering and oscillations. For the new gauge coupling $g_X$ in the range $(10^{-2} - 10^{-4})$ the model is shown to be consistent with the data. Possible ways of testing the model in $b$ physics, top and $Z$ decays, direct collider production and neutrino oscillation experiments, where one can observe nonstandard matter effects, are outlined. The choice of leptons to carry the new force is ambiguous, resulting in additional phenomenological implications, such as non-universality in semileptonic bottom decays. The proposed framework provides interesting connections between neutrino oscillations, flavor and collider physics.
Two-terminal transport measurements with cold atoms
Krinner, Sebastian; Esslinger, Tilman; Brantut, Jean-Philippe
In recent years, the ability of cold atom experiments to explore condensed-matter-related questions has dramatically progressed. Transport experiments, in particular, have expanded to the point in which conductance and other transport coefficients can now be measured in a way that is directly analogous to solid-state physics, extending cold-atom-based quantum simulations into the domain of quantum electronic devices. In this topical review, we describe the transport experiments performed with cold gases in the two-terminal configuration, with an emphasis on the specific features of cold atomic gases compared to solid-state physics. We present the experimental techniques and the main experimental findings, focusing on—but not restricted to—the recent experiments performed by our group. We finally discuss the perspectives opened up by this approach, the main technical and conceptual challenges for future developments, and potential applications in quantum simulation for transport phenomena and mesoscopic physics problems.
46 CFR 194.15-17 - Compressed gases other than inert gases.
... 46 Shipping 7 2010-10-01 2010-10-01 false Compressed gases other than inert gases. 194.15-17 Section 194.15-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OCEANOGRAPHIC RESEARCH VESSELS HANDLING, USE, AND CONTROL OF EXPLOSIVES AND OTHER HAZARDOUS MATERIALS Chemistry Laboratory and...
Broader perspectives for comparing different greenhouse gases.
Manning, Martin; Reisinger, Andy
Over the last 20 years, different greenhouse gases have been compared, in the context of climate change, primarily through the concept of global warming potentials (GWPs). This considers the climate forcing caused by pulse emissions and integrated over a fixed time horizon. Recent studies have shown that uncertainties in GWP values are significantly larger than previously thought and, while past literature in this area has raised alternative means of comparison, there is not yet any clear alternative. We propose that a broader framework for comparing greenhouse gases has become necessary and that this cannot be addressed by using simple fixed exchange rates. From a policy perspective, the framework needs to be clearly aligned with the goal of climate stabilization, and we show that comparisons between gases can be better addressed in this context by the forcing equivalence index (FEI). From a science perspective, a framework for comparing greenhouse gases should also consider the full range of processes that affect atmospheric composition and how these may alter for climate stabilization at different levels. We cover a basis for a broader approach to comparing greenhouse gases by summarizing the uncertainties in GWPs, linking those to uncertainties in the FEIs consistent with stabilization, and then to a framework for addressing uncertainties in the corresponding biogeochemical processes. © 2011 The Royal Society
Phosphorus {delta}-doped silicon: mixed-atom pseudopotentials and dopant disorder effects
Energy Technology Data Exchange (ETDEWEB)
Carter, Damien J; Marks, Nigel A [Nanochemistry Research Institute, Curtin University, PO Box U1987, Perth WA 6845 (Australia); Warschkow, Oliver; McKenzie, David R, E-mail: firstname.lastname@example.com [Centre for Quantum Computer Technology, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)
Within a full density functional theory framework we calculate the band structure and doping potential for phosphorus {delta}-doped silicon. We compare two different representations of the dopant plane; pseudo-atoms in which the nuclear charge is fractional between silicon and phosphorus, and explicit arrangements employing distinct silicon and phosphorus atoms. While the pseudo-atom approach offers several computational advantages, the explicit model calculations differ in a number of key points, including the valley splitting, the Fermi level and the width of the doping potential. These findings have implications for parameters used in device modelling.
Absorption of Soluble Gases by Atmospheric Nanoaerosols
Elperin, Tov; Krasovitov, Boris; Lushnikov, Alexey
We investigate mass transfer during absorption of atmospheric trace soluble gases by a single droplet whose size is comparable to the molecular mean free path in air at normal conditions. It is assumed that the trace reactant diffuses to the droplet surface and then reacts with the substances inside the droplet according to the first order rate law. Our analysis applies a flux-matching theory of transport processes in gases and assumes constant thermophysical properties of the gases and liquids. We derive an integral equation of Volterra type for the transient molecular flux density to a liquid droplet and solve it numerically. Numerical calculations are performed for absorption of sulfur dioxide (SO2), dinitrogen trioxide (N2O3) and chlorine (Cl2) by liquid nanoaerosols accompanied by chemical dissociation reaction. It is shown that during gas absorption by nanoaerosols the kinetic effects play significant role, and neglecting kinetic effects leads to significant overestimation of the soluble gas flux into a...
Directory of Open Access Journals (Sweden)
Dušica Stojanović
Full Text Available The greenhouse effect can be defined as the consequence of increased heating of the Earth's surface, as well as the lower atmosphere by carbon dioxide, water vapor, and other trace amounts gases. It is well-known that human industrial activities have released large amounts of greenhouse gases in the atmosphere, about 900 billion tons of carbon dioxide, and it is estimated that up to 450 billion are still in the atmosphere. In comparison to greenhouse gases water vapor is one of the greatest contributors to the greenhouse effect on Earth. Many projects, as does the PURGE project, have tendences to build on the already conducted research and to quantify the positive and negative impacts on health and wellbeing of the population with greenhouse gas reduction strategies that are curently being implemented and should be increasingly applied in various sectors and urban areas, having offices in Europe, China and India.
Energy Technology Data Exchange (ETDEWEB)
Park, Jong Gwan [I and Book, Seoul (Korea, Republic of)
This book has a lot of explanation of nuclear energy with articles. Their titles are the bad man likes atomic, the secret of atom, nuclear explosion, NPT?, the secret of uranium fuel rod, nuclear power plant vs nuclear bomb, I hate atomic, keep plutonium in control, atomic in peace and find out alternative energy.
Flammability characteristics of combustible gases and vapors
Energy Technology Data Exchange (ETDEWEB)
Zabetakis, M. G. [Bureau of Mines, Pittsburgh, PA (United States)
This is a summary of the available limit of flammability, autoignition and burning-rate data for more than 200 combustible gases and vapors in air and other oxidants, as well as of empirical rules and graphs that can be used to predict similar data for thousands of other combustibles under a variety of environmental conditions. Spec$c data are presented on the paraffinic, unsaturated, aromatic, and alicyclic hydrocarbons, alcohols, ethers, aldehydes, ketones, and sulfur compounds, and an assortment of fuels, fuel blends, hydraulic fluids, engine oils, and miscellaneous combustible gases and vapors.
Investigations into electrical discharges in gases
Klyarfel'D, B N
Investigations into Electrical Discharges in Gases is a compilation of scientific articles that covers the advances in the investigation of the fundamental processes occurring in electrical discharges in gases and vapors. The book details the different aspects of the whole life cycle of an arc, which include the initiation of a discharge, its transition into an arc, the lateral spread of the arc column, and the recovery of electric strength after extinction of an arc. The text also discusses the methods for the dynamic measurement of vapor density in the vicinity of electrical discharges, alon
Mitigation of greenhouse gases from agriculture
DEFF Research Database (Denmark)
Schils, R.L.M.; Ellis, J. L.; de Klein, C. A. M.
Models are widely used to simulate the emission of greenhouse gases (GHG). They help to identify knowledge gaps, estimate total emissions for inventories, develop mitigation options and policies, raise awareness and encourage adoption. These models vary in scale, scope and methodological approach....... The scale increases from field, manure storage or rumen via herd or farm to country or continent. The scope may be restricted to a single GHG or include all gases. Multidisciplinary models may include nutrients, other substances or socio-economic parameters. Mechanistic process-based models have been...
Spherulite Growth in GaSe Films
Hashimoto, Hidenori; Suzuki, Hiromichi
Thin film spherulites were crystallized by heating above 370°C in vacuum from the amorphous GaSe films prepared by flash evaporation. The spherulites are a sort of polycrystalline GaSe and the c-axes are formed finely along the radial direction of the spherulites. Activation energies of crystallization depended on film thickness of the spherulites and were 0.79 eV for 200 nm and 0.32 eV for 550 nm film thickness.
Measurement of sulphur gases in ambient air.
Lau, Y K
A gas chromatograph with a flame photometric detector is set up for the direct analysis of COS, H2S, CS2, SO2, CH3SH, C2H5SH in ambient air.Logarithmic transformation is used to counterbalance the non-linear nature of the detector response for the individual sulphur gases. A quality assurance procedure is described to compensate any variation of response during field measurement. The use of Tedlar bags for sampling COS, CS2, CH3SH, C2H5SH is acceptable despite the general conception that sulphur gases are unstable in Tedlar bags.
Gases and vacua handbook of vacuum physics
Beck, A H
Handbook of Vacuum Physics, Volume 1: Gases and Vacua presents three major topics, which are the fourth to sixth parts of this volume. These topics are the remarks on units of physical quantities; kinetic theory of gases and gaseous flow; and theory of vacuum diffusion pumps. The first topic aims to present concisely the significance of units of physical quantities, catering the need and interest of those who take measurements and make calculations in different fields of vacuum sciences. The technique and applications of this particular topic are also provided. The second main topic focuses sp
Origins of geothermal gases at Yellowstone
Lowenstern, Jacob B.; Bergfeld, Deborah; Evans, William C.; Hunt, Andrew G.
Gas emissions at the Yellowstone Plateau Volcanic Field (YPVF) reflect open-system mixing of gas species originating from diverse rock types, magmas, and crustal fluids, all combined in varying proportions at different thermal areas. Gases are not necessarily in chemical equilibrium with the waters through which they vent, especially in acid sulfate terrain where bubbles stream through stagnant acid water. Gases in adjacent thermal areas often can be differentiated by isotopic and gas ratios, and cannot be tied to one another solely by shallow processes such as boiling-induced fractionation of a parent liquid. Instead, they inherit unique gas ratios (e.g., CH4/He) from the dominant rock reservoirs where they originate, some of which underlie the Quaternary volcanic rocks. Steam/gas ratios (essentially H2O/CO2) of Yellowstone fumaroles correlate with Ar/He and N2/CO2, strongly suggesting that H2O/CO2 is controlled by addition of steam boiled from water rich in atmospheric gases. Moreover, H2O/CO2 varies systematically with geographic location, such that boiling is more enhanced in some areas than others. The δ13C and 3He/CO2 of gases reflect a dominant mantle origin for CO2 in Yellowstone gas. The mantle signature is most evident at Mud Volcano, which hosts gases with the lowest H2O/CO2, lowest CH4 concentrations and highest He isotope ratios (~16Ra), consistent with either a young subsurface intrusion or less input of crustal and meteoric gas than any other location at Yellowstone. Across the YPVF, He isotope ratios (3He/4He) inversely vary with He concentrations, and reflect varied amounts of long- stored, radiogenic He added to the magmatic endmember within the crust. Similarly, addition of CH4 from organic-rich sediments is common in the eastern thermal areas at Yellowstone. Overall, Yellowstone gases reflect addition of deep, high-temperature magmatic gas (CO2-rich), lower-temperatures crustal gases (4He- and CH4-bearing), and those gases (N2, Ne, Ar) added
Diffusive separation of noble gases and noble gas abundance patterns in sedimentary rocks
Energy Technology Data Exchange (ETDEWEB)
Torgersen, T.; Kennedy, B.M.; van Soest, M.C.
The mechanisms responsible for noble gas concentrations, abundance patterns, and strong retentivity in sedimentary lithologies remain poorly explained. Diffusion-controlled fractionation of noble gases is modeled and examined as an explanation for the absolute and relative abundances of noble gases observed in sediments. Since the physical properties of the noble gases are strong functions of atomic mass, the individual diffusion coefficients, adsorption coefficients and atomic radii combine to impede heavy noble gas (Xe) diffusion relative to light noble gas (Ne) diffusion. Filling of lithic grains/half-spaces by diffusive processes thus produces Ne enrichments in the early and middle stages of the filling process with F(Ne) values similar to that observed in volcanic glasses. Emptying lithic grains/half-spaces produces a Xe-enriched residual in the late (but not final) stages of the process producing F(Xe) values similar to that observed in shales. 'Exotic but unexceptional' shales that exhibit both F(Ne) and F(Xe) enrichments can be produced by incomplete emptying followed by incomplete filling. This mechanism is consistent with literature reported noble gas abundance patterns but may still require a separate mechanism for strong retention. A system of labyrinths-with-constrictions and/or C-, Si-nanotubes when combined with simple adsorption can result in stronger diffusive separation and non-steady-state enrichments that persist for longer times. Enhanced adsorption to multiple C atoms inside C-nanotubes as well as dangling functional groups closing the ends of nanotubes can provide potential mechanisms for 'strong retention'. We need new methods of examining noble gases in rocks to determine the role and function of angstrom-scale structures in both the diffusive enrichment process and the 'strong retention' process for noble gas abundances in terrestrial rocks.
DissipaÃÃo no Modelo Fermi-Ulam
Danila Fernandes Tavares de Sousa
Neste trabalho, revisitamos o modelo do acelerador de Fermi, tambÃm conhecido como modelo Fermi-Ulam. Este modelo consiste de uma partÃcula clÃssica de massa unitÃria que està confinada e colidindo elasticamente entre duas paredes rÃgidas, uma delas sendo fixa e a outra dependente do tempo. A descriÃÃo da dinÃmica à feita todas as vezes que a partÃcula colide com a parede mÃvel, de modo que o conhecimento dos valores da velocidade da partÃcula e do tempo no instante da colisÃo descrevem toda ...
What determines the Fermi wave vector of composite fermions?
Kamburov, D; Liu, Yang; Mueed, M A; Shayegan, M; Pfeiffer, L N; West, K W; Baldwin, K W
Composite fermions (CFs), exotic particles formed by pairing an even number of flux quanta to each electron, provide a fascinating description of phenomena exhibited by interacting two-dimensional electrons at high magnetic fields. At and near Landau level filling ν=1/2, CFs occupy a Fermi sea and exhibit commensurability effects when subjected to a periodic potential modulation. We observe a pronounced asymmetry in the magnetic field positions of the commensurability resistance minima of CFs with respect to the field at ν=1/2. This unexpected asymmetry is consistent with the CFs' Fermi wave vector being determined by the minority carriers in the lowest Landau level, and suggests a breaking of the particle-hole symmetry for CFs near ν=1/2.
The Fermi Science Support Center Data Servers and Archive
Reustle, Alexander; Fermi Science Support Center
The Fermi Science Support Center (FSSC) provides the scientific community with access to Fermi data and other products. The Gamma-Ray Burst Monitor (GBM) data is stored at NASA's High Energy Astrophysics Science Archive Research Center (HEASARC) and is accessible through their searchable Browse web interface. The Large Area Telescope (LAT) data is distributed through a custom FSSC interface where users can request all photons detected from a region on the sky over a specified time and energy range. Through its website the FSSC also provides planning and scheduling products, such as long and short term observing timelines, spacecraft position and attitude histories, and exposure maps. We present an overview of the different data products provided by the FSSC, how they can be accessed, and statistics on the archive usage since launch.
Properties of Fermi liquids with a finite range interaction
Energy Technology Data Exchange (ETDEWEB)
Nozieres, P. (Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France))
Following a suggestion of Khodel' and Shaginyan (KS), it is shown that a Hartree Fock description of Fermi liquids can lead to very strange results when the interaction has long range. For instance, the sharp drop of particle distribution at the Fermi level can be smeared over a finite k-range, with a flat plateau in the quasiparticle energy. In practice, such an effect appears as an artefact of the Hartree Fock approximation. The KS effect occurs only for an attraction, in which case it is hidden by superconductivity. Moreover, the enhanced quasiparticle collision rate makes the Hartree Fock approximation untenable. Finally, screening of a strong long range interaction is such that the instability threshold cannot be reached.
New approach to microscopic theory of normal Fermi systems
Energy Technology Data Exchange (ETDEWEB)
Khodel, V.A. (Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Moscow. Inst. Atomnoj Ehnergii); Shaginyan, V.R. (Leningrad Inst. of Nuclear Physics, Gatchina (USSR))
A new version of the normal Fermi system microscopic theory is suggested. A functional equation for the effective potential R of the quasiparticle interaction is obtained. Methods for the evaluation of R in terms of the particle interaction potential are discussed. It is shown that in the well-known local approximation, the functional equation for R is reduced to an integro-differential one. For a number of model examples for which the Monte Carlo equation of state is known, the local approximation proves to reproduce the Monte Carlo results to an accuracy of a few percent. The method developed is applied to superfluid Fermi systems. The equation for the evaluation of the gap in the single-particle excitation spectrum in terms of the interaction potential R is obtained. (orig.).
Unconventional fermi surface instabilities in the kagome Hubbard model.
Kiesel, Maximilian L; Platt, Christian; Thomale, Ronny
We investigate the competing Fermi surface instabilities in the kagome tight-binding model. Specifically, we consider on-site and short-range Hubbard interactions in the vicinity of van Hove filling of the dispersive kagome bands where the fermiology promotes the joint effect of enlarged density of states and nesting. The sublattice interference mechanism devised by Kiesel and Thomale [Phys. Rev. B 86, 121105 (2012)] allows us to explain the intricate interplay between ferromagnetic fluctuations and other ordering tendencies. On the basis of the functional renormalization group used to obtain an adequate low-energy theory description, we discover finite angular momentum spin and charge density wave order, a twofold degenerate d-wave Pomeranchuk instability, and f-wave superconductivity away from van Hove filling. Together, this makes the kagome Hubbard model the prototypical scenario for several unconventional Fermi surface instabilities.
Poisson-Fermi Formulation of Nonlocal Electrostatics in Electrolyte Solutions
Directory of Open Access Journals (Sweden)
Liu Jinn-Liang
Full Text Available We present a nonlocal electrostatic formulation of nonuniform ions and water molecules with interstitial voids that uses a Fermi-like distribution to account for steric and correlation efects in electrolyte solutions. The formulation is based on the volume exclusion of hard spheres leading to a steric potential and Maxwell's displacement field with Yukawa-type interactions resulting in a nonlocal electric potential. The classical Poisson-Boltzmann model fails to describe steric and correlation effects important in a variety of chemical and biological systems, especially in high field or large concentration conditions found in and near binding sites, ion channels, and electrodes. Steric effects and correlations are apparent when we compare nonlocal Poisson-Fermi results to Poisson-Boltzmann calculations in electric double layer and to experimental measurements on the selectivity of potassium channels for K+ over Na+.
Enhanced diphoton rates at Fermi and the LHC
Energy Technology Data Exchange (ETDEWEB)
Schmidt-Hoberg, Kai [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Staub, Florian [Bonn Univ. (Germany). Bethe Center for Theoretical Physics und Physikalisches Inst.; Winkler, Martin Wolfgang [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
We show that within MSSM singlet extensions the experimental hints beyond the standard model from the Fermi LAT telescope as well as from the LHC can be explained simultaneously while being consistent with all experimental constraints. In particular we present an example point which features a {proportional_to}130 GeV lightest neutralino with an annihilation cross section into photons consistent with the indication from the Fermi satellite with simultaneously the right relic abundance, a continuum photon spectrum consistent with observation, direct detection cross section below the experimental limits, electroweak observables consistent with experiment and a 125 GeV light Higgs boson with a slightly enhanced h{yields}{gamma}{gamma} rate.
A Southern Sky Survey with Fermi LAT and ASKAP
Energy Technology Data Exchange (ETDEWEB)
Cameron, Robert A.; /SLAC /KIPAC, Menlo Park
We present the prospects for a future joint gamma-ray and radio survey of southern hemisphere sources using the Fermi Large Area Telescope (LAT) and the upcoming Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope. ASKAP is a next generation radio telescope designed to perform surveys at GHz frequencies at a much higher survey speed than previous radio telescopes, and is scheduled to start engineering observations in 2011. The survey capabilities of both Fermi LAT and ASKAP are described, and the planned science surveys for ASKAP are summarized. We give some expected details of the Variable and Slow Transient (VAST) survey using ASKAP, which will search for transients on timescales from 5 seconds to years. Some observational properties of faint and transient sources seen at gamma-ray and radio wavelengths are summarized, and prospects and strategies for using ASKAP survey data for LAT source counterpart identification are summarized.
Instanton effects in ABJM theory from Fermi gas approach
Energy Technology Data Exchange (ETDEWEB)
Hatsuda, Yasuyuki [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie; Tokyo Institute of Technology (Japan). Dept. of Physics; Moriyama, Sanefumi [Nagoya Univ. (Japan). Kobayashi Maskawa Inst.; Nagoya Univ. (Japan). Graduate School of Mathematics; Okuyama, Kazumi [Shinshu Univ., Matsumoto, Nagano (Japan). Dept. of Physics
We study the instanton effects of the ABJM partition function using the Fermi gas formalism. We compute the exact values of the partition function at the Chern-Simons levels k=1, 2, 3, 4, 6 up to N=44, 20, 18, 16, 14 respectively, and extract non-perturbative corrections from these exact results. Fitting the resulting non-perturbative corrections by their expected forms from the Fermi gas, we determine unknown parameters in them. After separating the oscillating behavior of the grand potential, which originates in the periodicity of the grand partition function, and the worldsheet instanton contribution, which is computed from the topological string theory, we succeed in proposing an analytical expression for the leading D2-instanton correction. Just as the perturbative result, the instanton corrections to the partition function are expressed in terms of the Airy function.
Super-allowed Fermi beta-decay revisited
Wilkinson, D H
Analysis of J suppi=0 sup +->0 sup + super-allowed Fermi transitions is limited with respect to the precision of its outcome in terms of the Fermi coupling constant neither by the accuracy of the experimental input data nor by the confidence with which the radiative corrections can be applied but rather by knowledge of the nuclear mismatch: the subversion of isospin symmetry along the multiplets. Theoretical estimates of this mismatch differ considerably from to their direct nuclide-by-nuclide application results in an apparent clear violation of the hypothesis of conservation of the vector current and evident inconsistency with unitary of the Cabibbo-Kobayashi-Maskawa matrix. This paper pursues and elaborates the earlier suggestion that, in these unsatisfactory circumstances, the best procedure is to look to the experimental data themselves to determine and eliminate the mismatch by appropriate extrapolation to Z approx 0 where the mismatch falls away. This is done: (i) without any prior correction for misma...
Tan's distributions and Fermi-Huang pseudopotential in momentum space
DEFF Research Database (Denmark)
Valiente, Manuel
The long-standing question of finding the momentum representation for the s-wave zero-range interaction in three spatial dimensions is here solved. This is done by expressing a certain distribution, introduced in a formal way in [ S. Tan Ann. Phys. (NY) 323 2952 (2008)], explicitly. The resulting...... form of the Fourier-transformed pseudopotential remains very simple. Operator forms for the so-called Tan's selectors, which, together with Fermi-Huang pseudopotential, largely simplify the derivation of Tan's universal relations for the Fermi gas, are here derived and are also very simple. A momentum...... cutoff version of the pseudopotential is also provided, and with this no apparent contradiction to the notion of integrals in Tan's methods is left. The equivalence, even at the intermediate-step level, between the pseudopotential approach and momentum-space renormalization of the bare Dirac delta...
Traffic modifications on Routes Rutherford, Democrite and Fermi
The GS Department would like to inform you that until the end of December, the construction of Building 245 will result in the following traffic modifications: Traffic on Route Rutherford will be partially restricted in front of the construction site, Traffic on Route Democrite will be one-way towards Route Rutherford. Also, please note that due to construction work in front of Building 377, Route Fermi will be closed from Wednesday, 10 June until Friday, 7 August. Thank you for your understanding.
IceCube Constraints on the Fermi Bubbles
Sherf, Nimrod; Keshet, Uri; Gurwich, Ilya
We analyze the IceCube four-year neutrino data in search of a signal from the Fermi bubbles. No signal is found from the bubbles or from their dense shell, even when taking into account the softer background. This imposes a conservative ξ I IceCube neutrinos increases by ˜an order of magnitude, unless there is a
Processing GPS Receiver Data for Improved Fermi GLAST Navigation
Woodard, Mark A.
Fermi GLAST s 5-year mission objectives: a) Explore the most extreme environments in the Universe. b) Search for signs of new laws of physics and what composes the mysterious Dark Matter. c) Explain how black holes accelerate immense jets of material to nearly light speed. d) Help crack the mysteries of gamma-ray bursts. e) Answer long-standing questions across a broad range of topics, including solar flares, pulsars and the origin of cosmic rays.
Properties of Fermi liquids with a finite range interaction
Nozières, Philippe
Following a suggestion of Khodel' and Shaginyan (KS), it is shown that a Hartree Fock description of Fermi liquids can lead to very strange results when the interaction has long range. For instance, the sharp drop of particle distribution at the Fermi level can be smeared over a finite k-range, with a flat plateau in the quasiparticle energy. In practice, such an effect appears as an artefact of the Hartree Fock approximation. The KS effect occurs only for an attraction, in which case it is hidden by superconductivity. Moreover, the enhanced quasiparticle collision rate makes the Hartree Fock approximation untenable. Finally, screening of a strong long range interaction is such that the instability threshold cannot be reached. Partant d'une suggestion de Khodel' et Shaginyan (KS), on montre que la description d'un liquide de Fermi en Hartree Fock peut conduire à des résultats très étranges quand la portée de l'interaction est grande. Par exemple, la discontinuité de la distribution des particules au niveau de Fermi est étalée sur une bande de k finie, avec un plateau de l'énergie des quasiparticules. En fait, cet état est une conséquence de l'approximation de Hartree Fock. Il se produit seulement pour une attraction, auquel cas il est masqué par la supraconductivité. De plus, le renforcement des collisions entre quasiparticules rend l'approximation de Hartree Fock inutilisable. Enfin, l'écrantage d'une interaction forte et à longue portée ne permet pas d'atteindre le seuil d'instabilité.
Fermi-LAT: 4+ Years Out and Just Getting Started!
CERN. Geneva
The Fermi mission was launched into low Earth orbit in June, 2008. Now in its 5th year of data taking, the primary instrument, the Large Area Telescope (LAT), is now beginning to have a sufficient exposure to probe such fundamental issues as signals from Dark Matter. The achievements of the mission so far will be reviewed and a look towards what the next years could reveal will be presented.
High Energy Astrophysics with the Fermi Large Area Telescope
Hays, Elizabeth
This slide presentation reviews some of the findings of the Large Area Telescope (LAT) aboard the Fermi Observatory. It includes information about the LAT, and the Gamma-Ray Burst Monitor (GBM), detection of the quiet sun and the moon in gamma rays, Pulsars observed by the observatory, Globular Star Clusters, Active Galactic Nucleus, and Gamma-Ray Bursts, with specific information about GRB 080916C.
Nuclear Emergency Plan, Part VI: Enrico Fermi 2
Energy Technology Data Exchange (ETDEWEB)
Plan dealing with actions to be undertaken at the provincial and municipal levels in Ontario to deal with a nuclear emergency caused by the Enrico Fermi 2 nuclear plant in Monroe County, Michigan, U.S.A. The plan covers the operations of the participating organizations in both Michigan and Ontario; notification; phase I and II actions; necessary actions in case of liquid emissions; and emergency information and public direction.
Extended Thomas-Fermi expansion from nuclear linear response
Energy Technology Data Exchange (ETDEWEB)
Navarro, J. [IFIC, Centre Mixt CSIC, Universitat de Valencia, Avda Dr Moliner 50, E-46.100 Burjassot (Spain); Vinas, X. [Departamento Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, Diagonal 645, E-08028 Barcelona (Spain)
The coefficients of the successive h/2{pi}{sup 2} orders of the extended Thomas-Fermi expansion of the kinetic energy density are obtained to the leading order in the density inhomogeneities. This is done by comparing the corresponding static polarizability with the exact value in two cases: a non-interacting nuclear infinite system and symmetric nuclear matter with a Skyrme interaction. (author)
Relativistic extended Thomas-Fermi calculations of finite nuclei
Energy Technology Data Exchange (ETDEWEB)
Centelles, M.; Vinas, X.; Barranco, M. (Barcelona Univ. (Spain). Facultat de Fisica); Ohtsuka, N.; Faessler, Amand; Khoa, D.T.; Muether, H. (Tuebingen Univ. (Germany). Inst. fuer Theoretische Physik)
We have used for the first time a relativistic extended Thomas-Fermi method which includes up to (h/2{pi}){sup 2}-corrective terms to study the structure of finite nuclei. The potential part has been obtained from a local density approximation to Dirac-Brueckner calculations carried out with a realistic nucleon-nucleon potential. Some applications to fission barriers and optical potentials for heavy ion scattering are presented. (author).
Diagnosing alternative conceptions of Fermi energy among undergraduate students
Sharma, Sapna; Ahluwalia, Pardeep Kumar
Physics education researchers have scientifically established the fact that the understanding of new concepts and interpretation of incoming information are strongly influenced by the preexisting knowledge and beliefs of students, called epistemological beliefs. This can lead to a gap between what students actually learn and what the teacher expects them to learn. In a classroom, as a teacher, it is desirable that one tries to bridge this gap at least on the key concepts of a particular field which is being taught. One such key concept which crops up in statistical physics/solid-state physics courses, and around which the behaviour of materials is described, is Fermi energy (εF). In this paper, we present the results which emerged about misconceptions on Fermi energy in the process of administering a diagnostic tool called the Statistical Physics Concept Survey developed by the authors. It deals with eight themes of basic importance in learning undergraduate solid-state physics and statistical physics. The question items of the tool were put through well-established sequential processes: definition of themes, Delphi study, interview with students, drafting questions, administration, validity and reliability of the tool. The tool was administered to a group of undergraduate students and postgraduate students, in a pre-test and post-test design. In this paper, we have taken one of the themes i.e. Fermi energy of the diagnostic tool for our analysis and discussion. Students' responses and reasoning comments given during interview were analysed. This analysis helped us to identify prevailing misconceptions/learning gaps among students on this topic. How spreadsheets can be effectively used to remove the identified misconceptions and help appreciate the finer nuances while visualizing the behaviour of the system around Fermi energy, normally sidestepped both by the teachers and learners, is also presented in this paper.
Search for Gravitational Wave Counterparts with Fermi GBM
Hui, C. M.
The progenitor of short gamma-ray bursts (GRBs) is believed to be the merger of two compact objects. This type of events will also produce gravitational waves. Since the gravitational waves discovery by LIGO, the search for a joint detection with an electromagnetic counterpart has been ongoing. Fermi GBM detects approximately 40 short GRBs per year, and we have been expanding our search looking for faint events in the GBM data that did not trigger onboard.
Laser Spectroscopy of Antiprotonic Helium Atoms
%PS205 %title\\\\ \\\\Following the discovery of metastable antiprotonic helium atoms ($\\overline{p}He^{+} $) at KEK in 1991, systematic studies of their properties were made at LEAR from 1991 to 1996. In the first two years the lifetime of $\\overline{p}He^{+}$ in liquid and gaseous helium at various temperatures and pressures was measured and the effect of foreign gases on the lifetime of these atoms was investigated. Effects were also discovered which gave the antiproton a 14\\% longer lifetime in $^4$He than in $^3$He, and resulted in important differences in the shape of the annihilation time spectra in the two isotopes.\\\\ \\\\Since 1993 laser spectroscopy of the metastable $\\overline{p}He^{+}$ atoms became the main focus of PS205. Transitions were stimulated between metastable and non-metastable states of the $\\overline{p}He^{+}$ atom by firing a pulsed dye laser beam into the helium target every time an identified metastable atom was present (Figure 1). If the laser frequency matched the transition energy, the...
The First FERMI-LAT Gamma-Ray Burst Catalog
Ackermann, M.; Ajello, M.; Asano, K.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.;
In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy great than (20 MeV) gamma-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above approximately 20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.
Energy Technology Data Exchange (ETDEWEB)
Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Asano, K. [Interactive Research Center of Science, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551 (Japan); Axelsson, M. [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Baldini, L. [Università di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bechtol, K.; Bloom, E. D. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bhat, P. N. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Bissaldi, E. [Institut für Astro- und Teilchenphysik and Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck (Austria); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Bonnell, J.; Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bouvier, A., E-mail: firstname.lastname@example.com, E-mail: email@example.com [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); and others
In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (∼> 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ∼20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.
SU (2) lattice gauge theory simulations on Fermi GPUs
Cardoso, Nuno; Bicudo, Pedro
In this work we explore the performance of CUDA in quenched lattice SU (2) simulations. CUDA, NVIDIA Compute Unified Device Architecture, is a hardware and software architecture developed by NVIDIA for computing on the GPU. We present an analysis and performance comparison between the GPU and CPU in single and double precision. Analyses with multiple GPUs and two different architectures (G200 and Fermi architectures) are also presented. In order to obtain a high performance, the code must be optimized for the GPU architecture, i.e., an implementation that exploits the memory hierarchy of the CUDA programming model. We produce codes for the Monte Carlo generation of SU (2) lattice gauge configurations, for the mean plaquette, for the Polyakov Loop at finite T and for the Wilson loop. We also present results for the potential using many configurations (50,000) without smearing and almost 2000 configurations with APE smearing. With two Fermi GPUs we have achieved an excellent performance of 200× the speed over one CPU, in single precision, around 110 Gflops/s. We also find that, using the Fermi architecture, double precision computations for the static quark-antiquark potential are not much slower (less than 2× slower) than single precision computations.
Radio-weak BL Lac Objects in the Fermi Era
Massaro, F.; Marchesini, E. J.; D'Abrusco, R.; Masetti, N.; Andruchow, I.; Smith, Howard A.
The existence of "radio-weak BL Lac objects" (RWBLs) has been an open question, and has remained unsolved since the discovery that quasars could be radio-quiet or radio-loud. Recently, several groups identified RWBL candidates, mostly found while searching for low-energy counterparts of the unidentified or unassociated gamma-ray sources listed in the Fermi catalogs. Confirming RWBLs is a challenging task since they could be confused with white dwarfs (WDs) or weak emission line quasars (WELQs) when there are not sufficient data to precisely draw their broadband spectral energy distribution, and their classification is mainly based on a featureless optical spectra. Motivated by the recent discovery that Fermi BL Lacs appear to have very peculiar mid-IR emission, we show that it is possible to distinguish between WDs, WELQs, and BL Lacs using the [3.4]-[4.6]-[12] μm color-color plot built using the WISE magnitudes when the optical spectrum is available. On the basis of this analysis, we identify WISE J064459.38+603131 and WISE J141046.00+740511.2 as the first two genuine RWBLs, both potentially associated with Fermi sources. Finally, to strengthen our identification of these objects as true RWBLs, we present multifrequency observations for these two candidates to show that their spectral behavior is indeed consistent with that of the BL Lac population.
Are the surface Fermi arcs in Dirac semimetals topologically protected?
Kargarian, Mehdi; Randeria, Mohit; Lu, Yuan-Ming
Motivated by recent experiments probing anomalous surface states of Dirac semimetals (DSMs) Na3Bi and Cd3As2, we raise the question posed in the title. We find that, in marked contrast to Weyl semimetals, the gapless surface states of DSMs are not topologically protected in general, except on time-reversal-invariant planes of surface Brillouin zone. We first demonstrate this finding in a minimal four-band model with a pair of Dirac nodes at [Formula: see text] where gapless states on the side surfaces are protected only near [Formula: see text] We then validate our conclusions about the absence of a topological invariant protecting double Fermi arcs in DSMs, using a K-theory analysis for space groups of Na3Bi and Cd3As2 Generically, the arcs deform into a Fermi pocket, similar to the surface states of a topological insulator, and this pocket can merge into the projection of bulk Dirac Fermi surfaces as the chemical potential is varied. We make sharp predictions for the doping dependence of the surface states of a DSM that can be tested by angle-resolved photoemission spectroscopy and quantum oscillation experiments.
Dynamic structure function of some singular Fermi liquids
Varma, Chandra M.
The density correlations of some singular Fermi liquids with anomalous properties such as resistivity varying linearly with T at low temperatures and a T logT contribution to the entropy and thermopower are expected to be quite different from that in Landau Fermi liquids. A possible statistical mechanical model for the quantum-critical fluctuations in diverse systems with such properties is the 2D dissipative quantum XY model. Exact relations between the density correlations and singular irreducible vertices due to coupling of fermions to the topological excitations of the 2D dissipative quantum XY model are used to derive results which have become measurable only recently because of advances in experimental techniques. The density correlations are unusual at all momenta q and energy ω , from the hydrodynamic limit to that for large momenta and energy. The hydrodynamic limit together with the continuity equation gives the linear in T resistivity. The density correlations are almost independent of frequency up to a high-frequency cutoff for qZ B≳q ≫ω /vF ; qZ B is the Brillouin zone boundary and vF is the Fermi velocity. The results should be applicable to loop-current quantum criticality in cuprates, and to 2D Fe-based compounds near their antiferromagnetic quantum criticality. The relation of the results to the temperature and frequency dependent conductivity and to Raman response is also discussed.
Energy Technology Data Exchange (ETDEWEB)
Massaro, F.; Marchesini, E. J. [Dipartimento di Fisica, Università degli Studi di Torino (UniTO), via Pietro Giuria 1, I-10125 Torino (Italy); D'Abrusco, R.; Smith, Howard A. [Smithsonian Astrophysical Observatory, 60 Garden Street, 02138 Cambridge, MA (United States); Masetti, N. [INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129, Bologna (Italy); Andruchow, I. [Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA, La Plata (Argentina)
The existence of "radio-weak BL Lac objects" (RWBLs) has been an open question, and has remained unsolved since the discovery that quasars could be radio-quiet or radio-loud. Recently, several groups identified RWBL candidates, mostly found while searching for low-energy counterparts of the unidentified or unassociated gamma-ray sources listed in the Fermi catalogs. Confirming RWBLs is a challenging task since they could be confused with white dwarfs (WDs) or weak emission line quasars (WELQs) when there are not sufficient data to precisely draw their broadband spectral energy distribution, and their classification is mainly based on a featureless optical spectra. Motivated by the recent discovery that Fermi BL Lacs appear to have very peculiar mid-IR emission, we show that it is possible to distinguish between WDs, WELQs, and BL Lacs using the [3.4]–[4.6]–[12] μ m color–color plot built using the WISE magnitudes when the optical spectrum is available. On the basis of this analysis, we identify WISE J064459.38+603131 and WISE J141046.00+740511.2 as the first two genuine RWBLs, both potentially associated with Fermi sources. Finally, to strengthen our identification of these objects as true RWBLs, we present multifrequency observations for these two candidates to show that their spectral behavior is indeed consistent with that of the BL Lac population.
Fermi: The Gamma-Ray Large Area Telescope Mission Status
McEnery, Julie
Following its launch in June 2008, high-energy gamma-ray observations by the Fermi Gamma-ray Space Telescope have unveiled over 1000 new sources and opened an important and previously unexplored window on a wide variety of phenomena. These have included the discovery of an population of pulsars pulsing only in gamma rays; the detection of photons up to 10s of GeV from gamma-ray bursts, enhancing our understanding of the astrophysics of these powerful explosions; the detection of hundreds of active galaxies; a measurement of the high energy cosmic-ray electron spectrum which may imply the presence of nearby astrophysical particle accelerators; the determination of the diffuse gamma-ray emission with unprecedented accuracy and the constraints on phenomena such as supersymmetric dark-matter annihilations and exotic relics from the Big Bang. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from active galaxies and the discovery of transient sources in our galaxy. In this talk I will describe the current status of the Fermi observatory and review the science highlights from Fermi.
Fermi: The Gamma-Ray Large Area Space Telescope
McEnery, Julie
Following its launch in June 2008, high-energy gamma-ray observations by the Fermi Gamma-ray Space Telescope have unveiled over 1000 new sources and opened an important and previously unexplored window on a wide variety of phenomena. These have included the discovery of an population of pulsars pulsing only in gamma rays; the detection of photons up to 10s of GeV from gamma-ray bursts, enhancing our understanding of the astrophysics of these powerful explosions; the detection of hundreds of active galaxies; a measurement of the high energy cosmic-ray electron spectrum which may imply the presence of nearby astrophysical particle accelerators; the determination of the diffuse gamma-ray emission with unprecedented accuracy and the constraints on phenomena such as supersymmetric dark-matter annihilations and exotic relics from the Big Bang. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from active galaxies and the discovery of transient sources in our galaxy. In this talk I will describe the current status of the Fermi observatory and review the science highlights from Fermi.
Fermi: The Gamma-Ray Large Area Telescope
McEnery, Julie
Following its launch in June 2008, high-energy gamma-ray observations by the Fermi Gamma-ray Space Telescope have unveiled over 1000 new sources and opened an important and previously unexplored window on a wide variety of phenomena. These have included the discovery of an population of pulsars pulsing only in gamma rays; the detection of photons up to 10s of GeV from gamma-ray bursts, enhancing our understanding of the astrophysics of these powerful explosions; the detection of hundreds of active galaxies; a measurement of the high energy cosmic-ray electron spectrum which may imply the presence of nearby astrophysical particle accelerators; the determination of the diffuse gamma-ray emission with unprecedented accuracy and the constraints on phenomena such as supersymmetric dark-matter annihilations and exotic relics from the Big Bang. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from active galaxies and the discovery of transient sources in our galaxy. In this talk I will describe the current status of the Fermi observatory and review the science highlights from Fermi.
Infrared scintillation in gases, liquids and crystals
Belogurov, S.; Bressi, G; Carugno, G.; Conti, E; Iannuzzi, D; Meneguzzo, AT
We report about experimental evidences of infrared scintillation in gaseous, liquid and crystal samples. We firstly studied noble gases at room temperature and near atmospheric pressure in the wavelength range between 0.7 and 1.81 mum. Ar gas emits infrared photons when irradiated by a proton beam.