Meson fluctuations and thermodynamics of the Polyakov loop extended quark-meson model

TL;DR

This paper investigates the thermodynamics and phase structure of the Polyakov loop-extended quark-meson model using the functional renormalization group, highlighting the effects of fluctuations and gluonic backgrounds on quark number fluctuations.

Contribution

It introduces a truncation scheme for the effective action and derives flow equations for thermodynamic potentials at finite temperature and density.

Findings

Fluctuations and gluonic backgrounds significantly influence quark number fluctuations.

The kurtosis of quark fluctuations depends on the pion mass and smooths near the crossover.

Background fields modify the properties of net-quark number density fluctuations.

Abstract

Thermodynamics and the phase structure of the Polyakov loop-extended two flavor chiral quark-meson model (PQM) are explored. The analysis of the PQM model is based on the functional renormalization group (FRG) method. An appropriate truncation of the effective action with quarks coupled to background gluonic fields is introduced. Within this scheme, we derive the renormalization group flow equation for the scale-dependent thermodynamic potential at finite temperature and density in the presence of a symmetry breaking external field. The influence of fluctuations and of the background gluon field on the properties of net-quark number density fluctuations and their higher moments is explored. We study the dependence of the kurtosis of quark number fluctuations on the pion mass and show that, in the presence of a symmetry breaking term, the fluctuations lead to a smoothing of observables near the crossover transition.