Nonperturbative thermodynamics of an interacting Bose gas

Abstract

We discuss the thermodynamics of a non-relativistic gas of bosons with a local repulsive interaction. In particular, we compute the temperature and density dependence of pressure, energy and entropy-density, superfluid and condensate-fraction, correlation length, specific heat, isothermal and adiabatic compressibility and various sound velocities. The T->0 limit approaches the quantum phase transition, while the universal critical behavior of a classical second order phase transition in the O(2) universality class determines the region around the critical temperature. Our non-perturbative flow equations based on exact functional renormalization cover all regions in the phase diagram.