Resummation of infrared divergencies in the theory of atomic Bose gases

TL;DR

This paper develops a strong-coupling resummation method for atomic Bose gases that addresses infrared divergences, improving the understanding of key physical properties beyond the Bogoliubov approximation.

Contribution

It introduces a systematic strong-coupling approach with renormalization-group improvements for analyzing Bose gases beyond weak coupling.

Findings

Accurate calculation of chemical potential and contact in strong coupling regimes

Determination of the speed of sound and condensate density beyond Bogoliubov theory

Reduction to Bogoliubov theory in the weak-coupling limit

Abstract

We present a general strong-coupling approach for the description of an atomic Bose gas beyond the Bogoliubov approximation, when infrared divergences start to occur that need to be resummed exactly. We consider the determination of several important physical properties of the Bose gas, namely the chemical potential, the contact, the speed of sound, the condensate density, the effective interatomic interaction and the three-body recombination rate. It is shown how the approach can be systematically improved with renormalization-group methods and how it reduces to the Bogoliubov theory in the weak-coupling limit.