Pion superfluidity beyond mean field approximation in the Nambu–Jona-Lasinio model

Abstract

We investigate pion superfluidity in the frame of a 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. Because of the meson fluctuations, the Sarma phase which exists at the mean field level is washed away, and the Bose-Einstein condensation region at low isospin density is highly suppressed.