Signatures of L\'evy flights with annealed disorder
  We present theoretical and experimental results of L\'evy flights of light originating from a random walk of photons in a hot atomic vapor. In contrast to systems with quenched disorder, this system does not present any correlations between the position and the step length of the random walk. In an analytical model based on microscopic first principles including Doppler broadening we find anomalous L\'evy-type superdiffusion corresponding to a single-step size distribution P(x) proportional to x^(-1-alpha), with alpha=1. We show that this step size distribution leads to a violation of Ohm's law [T_(diff) proportional to L^(-alpha/2) different from 1/L], as expected for a L\'evy walk of independent steps. Furthermore the spatial profile of the transmitted light develops power law tails [I(r) proportional to r^(-3-alpha)]. In an experiment using a slab geometry with hot rubidium vapor, we measured the total diffuse transmission T_(diff) and the spatial profile of the transmitted light T_{diff}(r). We obtained the microscopic L\'evy parameter alpha under macroscopic multiple scattering conditions paving the way to investigation of L\'evy flights in different atomic physics and astrophysics systems. 
Q. Baudouin, R. Pierrat, A. Eloy, E.J. Nunes-Pereira, P.-A. Cuniasse,   N. Mercadier and R. Kaiser
physics.optics