2020/07/31 by Sergey V. Tarasov, S. V. Tarasov, Vl. V. Kocharovsky +3 · 15 citations
Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #Bose gas #Bose–Einstein condensate #Cold Atom Physics and Bose-Einstein Condensates #Crossover #Fermi gas #Gaussian #Ideal gas #Mesoscopic physics #Physics #Quantum #Quantum fluctuation #Quantum mechanics #Quantum, superfluid, helium dynamics #Statistical physics #Thermodynamic limit #cond-mat.quant-gas
paper · pdf · doi:10.1103/physreva.102.043315
published in Physical Review A 102(4) (American Physical Society) · This is a replacement of the first arXiv version (from July 30th, 2020) with misprints corrected
openalex publication_date 2020/10/13 · arxiv created 2021/02/25 · arxiv updated 2021/03/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We calculate the Bose-Einstein-condensate (BEC) occupation statistics vs the interparticle interaction in a dilute gas with a nonuniform condensate in a box trap within the Bogoliubov approach. The results are compared against the previously found BEC-occupation statistics in (i) an ideal gas and (ii) a weakly interacting gas with a uniform condensate. In particular, we reveal and explicitly describe an appearance of a nontrivial transition from the ideal gas to the Thomas-Fermi regime. The results include finding the main regimes of the BEC statistics---the anomalous non-Gaussian thermally dominated fluctuations and the Gaussian quantum-dominated fluctuations---as well as a crossover between them and their manifestations in a mesoscopic system. Remarkably, we show that the effect of the boundary conditions, imposed at the box trap, on the BEC fluctuations does not vanish in the thermodynamic limit of a macroscopic system even in the presence of the interparticle interactions. Finally, we discuss a challenging problem of an experimental verification of the theory of the BEC fluctuations addressing a much deeper level of the many-body statistical physics than usually studied quantities related to the mean condensate occupation.