Large Fluctuations for Spatial Diffusion of Cold Atoms

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We use a new approach to study the large fluctuations of a heavy-tailed system, 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 falloff of the density of thin-tailed systems. Here we investigate the spatial density Pt(x) of laser-cooled atoms, where at intermediate length scales the shape is fat tailed. We focus 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 with the recently proposed non-normalized infinite-covariant density approach. The small and large fluctuations give rise to a bifractal nature of the spreading packet. We derive general relations which extend our theory to a class of systems with multifractal moments.

Original languageEnglish
Article number260601
JournalPhysical Review Letters
Issue number26
StatePublished - 30 Jun 2017

Bibliographical note

Publisher Copyright:
© 2017 American Physical Society.


This work was supported by the Israel Science Foundation

FundersFunder number
Israel Science Foundation


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