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Microcanonical and Canonical Fluctuations in atomic Bose-Einstein Condensates -- Fock state sampling approach

by Maciej Bartłomiej Kruk, Dawid Hryniuk, Mick Kristensen, Toke Vibel, Krzysztof Pawłowski, Jan Arlt, Kazimierz Rzążewski

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Submission summary

Authors (as registered SciPost users): Maciej Kruk
Submission information
Preprint Link: scipost_202206_00011v2  (pdf)
Date accepted: 2022-11-28
Date submitted: 2022-09-15 15:02
Submitted by: Kruk, Maciej
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
  • Quantum Physics
Approach: Theoretical


The fluctuations of the atom number between a Bose-Einstein condensate and the surrounding thermal gas have been the subject of a long standing theoretical debate. This discussion is centered around the appropriate thermodynamic ensemble to be used for theoretical predictions and the effect of interactions on the observed fluctuations. Here we introduce the so-called Fock state sampling method to solve this classic problem of current experimental interest for weakly interacting gases. A suppression of the predicted peak fluctuations is observed when using a microcanonical with respect to a canonical ensemble. Moreover, interactions lead to a shift of the temperature of peak fluctuations for harmonically trapped gases. The absolute size of the fluctuations furthermore depends on the total number of atoms and the aspect ratio of the trapping potential. Due to the interplay of these effect, there is no universal suppression or enhancement of fluctuations.

Published as SciPost Phys. 14, 036 (2023)

Reports on this Submission

Anonymous Report 1 on 2022-9-24 (Invited Report)


I would like to thank the Authors for their response to my questions. In the revised manuscript, they have fully addressed my remarks, so that I recommend publication of the manuscript in its current form in SciPost Physics.

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