Two-dimensional weakly interacting Bose gas in the fluctuation region

Nikolai Prokof'ev, University of Massachusetts - Amherst
Boris Svistunov, University of Massachusetts - Amherst

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This is the pre-published version harvested from ArXiv. The published version is located at http://pra.aps.org/abstract/PRA/v66/i4/e043608

Abstract

We study the crossover between the mean-field and critical behavior of the two-dimensional Bose gas throughout the fluctuation region of the Berezinskii-Kosterlitz-Thouless phase transition point. We argue that this crossover is described by universal (for all weakly interacting |ψ|4 models) relations between thermodynamic parameters of the system, including superfluid and quasicondensate densities. We establish these relations with high-precision Monte Carlo simulations of the classical |ψ|4 model on a lattice, and check their asymptotic forms against analytic expressions derived on the basis of the mean-field theory.