Cosmology and Gravity

The Physics & Astronomy Department is engaged in a broad range of research that explores the nature of gravity and the origin and evolution of the Universe.  Theoretical research is conducted on general relativity, alternative-gravity theories, gravitational-wave physics and astrophysics, physical and early-Universe cosmology, and dark matter and dark energy.  Relevant experimental/observational work includes direct searches for dark matter, measurements of the cosmic expansion history, galaxy surveys, and cosmic-microwave-background measurements.

Nima Arkani-Hamed

Nima Arkani-Hamed

A professor at the Institute for Advance Study, Arkani-Hamed is also a Visiting Professor in the Department of Physics and Astronomy at Johns Hopkins. Arkani-Hamed is a particle theorist with broad interests, among them the physics behind inflation and the nature of dark matter. Arkani-Hamed is also currently pursuing fundamental new paradigms that may ultimately supplant our notions of space and time.

Ibrahima Bah


Bah is a theoretical physicist with a general research interest is in theoretical high-energy physics and cosmology. He explores the relations between quantum field theories, string theory and gravity via the framework of holography. Bah is also interested in fundamental aspect of black holes and their role in nature. His research work is part of a larger research program in high-energy physics whose main goal is to understand a quantum theory of gravity.

Charles Bennett

Chuck Bennett

Bennett is an experimental cosmologist perhaps best known for his role as Principal Investigator of NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), the satellite experiment that transformed our view of the Universe and the nature of its contents. Bennett is now co-leading (with Prof. Toby Marriage) the CLASS (Cosmology Large-Angular-Scale Surveyor) experiment which provides a unique avenue toward extracting information about inflation from the polarization of the cosmic microwave background. He is also building up to study the properties of the dark Universe as a member of the Euclid science consortium and of the Subaru Prime Focus Spectrograph (SPFS).

Emanuele Berti


Berti is a theoretical physicist who specializes in gravitational physics and gravitational-wave astronomy. His research interests include the structure, stability, dynamics and formation of black holes and neutron stars; gravitational-wave signatures of modified theories of gravity and physics beyond the Standard Model; using gravitational waves to understand black hole binary astrophysics and cosmology; and preparing for the challenge of detecting gravitational waves in space with LISA.

Marc Kamionkowski


Kamionkowski is a theoretical cosmologist with interests in inflation, dark energy, dark matter, and beyond. He is known largely for his work on dark matter and for the development of ideas that have motivated several generations of cosmic microwave background experiments. He is currently exploring new ideas for dark energy, dark matter, and inflation and news ways to test these ideas with a variety of astronomical observations and laboratory tests.

David Kaplan

David Kaplan

David Kaplan is a particle theorist whose wide interests include several subjects in cosmology. He is responsible for some of the most inventive and influential recent ideas for dark matter, including several that relate the origin of dark matter to that of the ordinary atomic matter of which we are composed. Kaplan is also known for his role as producer (and co-star) of “Particle Fever,” a feature-length documentary that follows the discovery of the Higgs boson at the Large Hadron Collider. Kaplan is currently exploring several new ideas for dark matter and new strategies for dark-matter detection.

Jared Kaplan

Jared Kaplan

Jared Kaplan is a particle theorist of remarkably broad interests that extend from condensed-matter theory to the early Universe.  He is known in the world of cosmology as co-creator of the effective field theory of inflation, a novel and powerful way to look at inflation, and for his work on dark matter.  His current work on black-hole physics in unusual spacetimes holds promise to elucidate the fundamental physics that may underlie inflation.

Toby Marriage

Toby Marriage

Marriage is an experimental cosmologist who before arriving at Johns Hopkins played a central role in the development, fielding, analysis pipeline, and science results from the Atacama Cosmology Telescope.  Chief among the results that he contributed to are measurements of cosmological parameters and studies of galaxy clusters.  He is currently co-leading (with Chuck Bennett) the CLASS (Cosmology Large-Angular-Scale Surveyor) experiment which provides a unique avenue toward extracting information about inflation from the polarization of the cosmic microwave background.

Brice Ménard

Brice Menard

Ménard is an observational cosmologist who specializes in distilling novel and important science results from large astronomical data sets.  This work has led to major advances in our ability to determine the distribution of dark matter in the Universe and the discovery of vast reservoirs of interstellar dust in galactic halos.  Ménard is currently developing a new approach to determine cosmic distances, a technique that is likely to considerably augment how science is done with future cosmic surveys.  He will also study the properties of the dark Universe as a member of the Euclid science consortium and of the Subaru Prime Focus Spectrograph (SPFS).

Surjeet Rajendran


Rajendran’s scholarly interests are in theoretical physics with a strong focus on physics beyond the standard model. Prior to coming to Hopkins, he was the Henry Shenker Professor of Physics at the University of California, Berkeley. He holds a PhD in physics from Stanford University.

Adam Riess

Adam Riess headshot

Riess is an observational cosmologist interested in measurements of the cosmic expansion history.  He was one of the key players in the 1998 discovery of accelerated cosmic expansion, which suggests that the Universe is filled with some negative-pressure “dark energy” that drives galaxies away from each other.  His work since then has placed important constraints on the nature of this dark energy.  He has also been leading an array of projects that provide the most stringent constraints to the Hubble constant, the parameter that measures the expansion rate of the Universe today.

Joseph Silk

Joseph Silk

Silk, who splits his time between Johns Hopkins, Oxford University, and the Institut d’Astrophysique in Paris, is one of the grey eminences of cosmology, with nearly half a century of contributions to a stunning variety of subjects in cosmology, physics, and astronomy.  This includes pioneering work on the cosmic microwave background and ideas that have motivated a variety of the most significant current experimental efforts to detect dark matter.  Silk currently works on a broad array of subjects, including dark matter, the physics of black holes, inflation, and galaxy formation.

Danielle Speller

Danielle Speller

Speller is a researcher in experimental nuclear and particle astrophysics. Her work centers on understanding the nature of matter and mass through low-energy, cryogenic searches for physics beyond the standard model. Professor Speller is a collaborator on both the Cryogenic Underground Observatory for Rare Events (CUORE) and the Haloscope at Yale Sensitive to Axion Cold dark matter (HAYSTAC), as well as related R&D projects. Her graduate work was with the Super Cryogenic Dark Matter Search experiment (SuperCDMS).

Alex Szalay

alex szalay

Szalay’s career has spanned an enormous range, beginning with important early theoretical contributions to particle astrophysics and cosmic statistics.  He was the chief architect of the Sloan Digital Sky Survey Data Archive and has become known as one of the chief pioneers of big-data astronomy.  His interests in big data have evolved into an array of subjects within computational astrophysics and to areas of science well beyond astrophysics.  His current research includes work on the large-scale structure of the Universe, data-archiving and data-mining techniques, and the mechanisms for doing science with future cosmology surveys.