Thermodynamics of (2+1)-flavor strongly interacting matter at nonzero isospin

TL;DR

This paper explores the phase structure of strongly interacting matter with nonzero isospin using an unquenched Polyakov-Quark-Meson model, comparing results with lattice data and highlighting the importance of pion mass effects.

Contribution

It provides a detailed analysis of the thermodynamics of (2+1)-flavor matter at nonzero isospin within a specific effective model, including comparisons to lattice results.

Findings

Pressure changes moderately with isospin at zero baryon chemical potential.

Chiral condensate decreases significantly with increasing isospin.

The pion mass significantly influences the transition line curvature.

Abstract

We investigate the phase structure of strongly interacting matter at non-vanishing isospin before the onset of pion condensation in the framework of the unquenched Polyakov-Quark-Meson model with 2+1 quark flavors. We show results for the order parameters and all relevant thermodynamic quantities. In particular, we obtain a moderate change of the pressure with isospin at vanishing baryon chemical potential, whereas the chiral condensate decreases more appreciably. We compare the effective model to recent lattice data for the decrease of the pseudo-critical temperature with the isospin chemical potential. We also demonstrate the major role played by the value of the pion mass in the curvature of the transition line, and the need for lattice results with a physical pion mass. Limitations of the model at nonzero chemical potential are also discussed.