Condensate statistics in interacting Bose gases: exact results

TL;DR

This paper applies a novel Quantum Monte Carlo method to obtain exact condensate occupation statistics in a weakly interacting 1D Bose gas across various temperatures, confirming the accuracy of number-conserving Bogoliubov theory in certain regimes.

Contribution

It introduces an alternative Monte Carlo approach for exact calculations of condensate statistics in interacting Bose gases, extending analysis across the critical temperature region.

Findings

Quantum Monte Carlo method yields exact occupation statistics.

Number-conserving Bogoliubov theory is accurate when non-condensed fraction is small.

Results span temperatures below the trap level spacing.

Abstract

Recently, a Quantum Monte Carlo method alternative to the Path Integral Monte Carlo method was developed for the numerical solution of the N-boson problem; it is based on the stochastic evolution of classical fields. Here we apply it to obtain exact results for the occupation statistics of the condensate mode in a weakly interacting trapped one-dimensional Bose gas. The temperature is varied across the critical region down to temperatures lower than the trap level spacing. We verify that the number-conserving Bogoliubov theory gives accurate predictions provided that the non-condensed fraction is small.