The Fock States Sampling method at work




Center for Theoretical Physics PAS

February 8, 2023 12:30 PM

Thermal fluctuations of Bose-Einstein condensate are of interest ever since E. Schrödinger noticed their dependence on the choice of a statistical ensemble. Widely used the grand statistical ensemble, when applied to an isolated system yielding unphysical results. The problem of fluctuations was a hot topic after the first experiments on BEC. Asymptotic results were obtained and recurrence relations were derived for partition functions in microcanonical and canonical ensembles. The role of weak collisions remains controversial. Recently, the fluctuations were finally measured by the group of Jan Arlt from Aarhus. We are providing theoretical background. In particular, in we argue that the experiment unveiled for the first time microcanonical fluctuations of the condensate. We developed a novel method of computing the statistics of the non-zero temperature properties of the Bose gas, named the Fock States Sampling method, that gives access to both, canonical and microcanonical statistics for up to 100 000 particles.

The method is also applicable to the weakly interacting gas trapped in a box. In this case, results for the interaction-induced shifts of the critical temperature will be revisited.

Thisis a hybrid event:

Al. Lotników 32/46, Warsaw, Room D 

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