Title: Large fluctuations for spatial diffusion of cold atoms
Author: Erez Aghion
We study the large fluctuations of heavy-tailed systems, where the standard large-deviations principle does not apply. Large-deviations theory deals with tails of probability distributions and the rare events of random processes, for example spreading packets of particles. Mathematically, it concerns the exponential fall-off of the density of thin-tailed systems.
In a recent PRL (published in 2017) we investigated the spatial density P_t(x) of laser-cooled atoms, where at intermediate length scales the shape is fat-tailed. We focused on the rare events beyond this range, which dominate important statistical properties of the system. Through a novel friction mechanism induced by the laser fields, the density is explored using the nonnormalized infinite-covariant density approach. The small and large fluctuations give rise to a bi-fractal nature of the spreading packet.