Abstract
Thermodynamics and the phase structure of the Polyakov loop-extended two flavors chiral quark--meson (PQM) model is explored beyond the mean-field approximation. The analysis of the PQM model is based on the functional renormalization group (FRG) method. We formulate and solve the renormalization group flow equation for the scale-dependent thermodynamic potential in the presence of the gluonic background field at finite temperature and density. We determine the phase diagram of the PQM model in the FRG approach and discuss its modification in comparison with the one obtained under the mean-field approximation. We focus on properties of the net-quark number density fluctuations as well as their higher moments and discuss the influence of non-perturbative effects on their properties near the chiral crossover transition. We show, that with an increasing net-quark number density the higher order moments exhibit a peculiar structure near the phase transition. We also consider ratios of different moments of the net-quark number density and discuss their role as probes of deconfinement and chiral phase transitions.
Highlights
Thermodynamic properties of strongly interacting matter at nonzero baryon density and high temperature have been explored numerically within lattice quantum chromodynamics (LQCD) [1,2,3]
The analysis of the Polyakov loop-extended two-flavor chiral quark-meson (PQM) model is based on the functional renormalization group (FRG) method
We extend our previous work [26] to nonzero chemical potential and locate the phase boundary and the critical end point (CEP) by exploring the dependence of the chiral order parameter and the quark number susceptibility on the thermodynamic variables
Summary
Thermodynamic properties of strongly interacting matter at nonzero baryon density and high temperature have been explored numerically within lattice quantum chromodynamics (LQCD) [1,2,3]. The properties of low-energy hadrons as well as the nature of the chiral phase transition at finite temperature and density have been studied intensively in such effective models. The Polyakov loop-extended Nambu-Jona-Lasinio (PNJL) [9] and quark-meson (PQM) [15] models reproduce essential features of the QCD thermodynamics already in the mean-field approximation. To correctly account for the critical behavior and scaling properties near the chiral phase transition, it is necessary to go beyond the mean-field approximation and include fluctuations and nonperturbative dynamics The cumulants of the net-quark number density (cn) are computed at finite temperature and chemical potential, including the effects of mesonic fluctuations. We summarize the results for the various susceptibilities near the chiral phase transition at finite net-quark density in the Landau (mean-field) and scaling theories
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