Influence of dynamical screening of four-quarks interaction on the chiral phase diagram

TL;DR

This paper studies how medium-dependent screening of four-quark interactions affects the chiral phase diagram in an effective QCD-inspired model, revealing temperature-dependent shifts and the need for additional effects at low temperatures.

Contribution

It introduces a medium-dependent coupling in a chiral model that accounts for screening effects, impacting the chiral phase transition and susceptibility behavior.

Findings

Chiral crossover temperature aligns with LQCD at low density.

Enhanced divergence of chiral susceptibility at the critical point.

Transition occurs at unphysically small chemical potential at zero temperature.

Abstract

We investigate the effect of screening of the four-quarks contact interactions by the ring diagram at finite temperature and density in an effective chiral model inspired by QCD in the Coulomb gauge. As a consequence, a medium-dependent coupling naturally emerges which, in a class of chiral models, brings the chiral crossover temperature down to the value calculated in LQCD at low net-baryon density. Furthermore, it implies a stronger divergence of the chiral susceptibility at the critical point compared to the mean-field dynamics. At vanishing temperature, however, the transition sets in at unphysically small chemical potential, indicating a need for additional effects to compensate for the screening strength. We discuss the properties of an effective potential for a class of models described by momentum-independent gap equations. In particular, we introduce the method to construct an approximate effective potential from the gap equations to determine the location of the first-order phase transition.