Three-dimensional QCD phase diagram in the pNJL model

TL;DR

This study uses the three-flavor pNJL model to map the three-dimensional QCD phase diagram, revealing how the Polyakov loop influences phase boundaries and critical points, thus providing more reliable predictions of QCD phases.

Contribution

It extends the NJL model by incorporating the Polyakov loop, significantly enlarging phase regions and shifting critical points in the QCD phase diagram.

Findings

Polyakov loop enlarges pion superfluid and Sarma phase regions.

Critical end points occur at higher temperatures with Polyakov loop.

The model offers more reliable predictions of QCD phases.

Abstract

Based on the three-flavor Polyakov-looped Nambu$-$Jona-Lasinio (pNJL) model, we have studied the structure of the three-dimensional QCD phase diagram with respect to the temperature, the baryon chemical potential, and the isospin chemical potential, by investigating the interplay among the chiral quark condensate, the pion condensate, and the Polyakov loop. While the pNJL model leads to qualitatively similar structure of the normal quark phase, the pion superfluid phase, and the Sarma phase as well as their phase boundaries, when compared to the NJL model, the inclusion of the Polyakov loop enlarges considerably the areas of the pion superfluid phase and the Sarma phase, and leads to critical end points at higher temperatures. With the contribution of the gluon dynamics effectively included, the present study is expected to give a more reliable prediction of the three-dimensional QCD phase diagram compared to that in the NJL model.