Pion Superfluidity beyond Mean Field Approximation In Nambu--Jona-Lasinio Model

TL;DR

This paper explores pion superfluidity using the Nambu--Jona-Lasinio model beyond mean field, revealing that meson fluctuations eliminate the Sarma phase and suppress Bose-Einstein condensation at low isospin density.

Contribution

It extends the analysis of pion superfluidity beyond mean field by including meson fluctuations in the NJL model at finite temperature and density.

Findings

Meson fluctuations wash out the Sarma phase.

Bose-Einstein condensation is highly suppressed at low isospin density.

The study provides a more accurate thermodynamic description of pion superfluidity.

Abstract

We investigate pion superfluidity in the frame of two flavor Nambu--Jona-Lasinio model beyond mean field approximation. We calculate the thermodynamics to the next to leading order in an expansion in the inverse number of colors, including both quark and meson contributions at finite temperature and baryon and isospin density. Due to the meson fluctuations, the Sarma phase which exists at mean field level is washed away, and the Bose-Einstein condensation region at low isospin density is highly suppressed.