Stability of the homogeneous Bose-Einstein condensate at large gas parameter

TL;DR

This paper investigates the stability of a homogeneous Bose-Einstein condensate with repulsive interactions, showing it becomes unstable beyond a critical gas parameter, and provides quantum corrections to key properties.

Contribution

It introduces a self-consistent variational perturbation approach to analyze BEC stability and quantum corrections beyond standard approximations.

Findings

BEC becomes unstable when gamma exceeds ~0.01

Quantum corrections to energy density, chemical potential, and pressure are derived

The approach improves understanding of BEC properties at large gas parameters

Abstract

The properties of the uniform Bose gas is studied within the optimized variational perturbation theory (Gaussian approximation) in a self-consistent way. It is shown that the atomic BEC with a repulsive interaction becomes unstable when the gas parameter gamma=rho a^3 exceeds a critical value gamma_{crit} ~ 0.01. The quantum corrections beyond the Bogoliubov-Popov approximation to the energy density, chemical potential and pressure in powers of gamma expansions are presented.