Modeling the QCD Equation of State Throughout the Thermal Deconfining Phase Transition from Hadronic Matter to a Quark–Gluon Plasma

Abstract

This work investigates the thermal deconfining phase transition from a hadronic gas composed of massive pions to a quark–gluon plasma (QGP) described by the Polyakov– Nambu–Jona-Lasinio (PNJL) model with two light quark flavors. The PNJL model extends the Nambu–Jona-Lasinio (NJL) approach, including chiral symmetry dynamics and the Polyakov loop, allowing a more realistic description of the QGP phase. A temperature-dependent switching function (SF) is used to ensure a smooth crossover between the hadronic and QGP phases. We analyze the temperature dependence of key thermodynamic quantities, including the pressure, energy density, entropy density, and the speed of sound squared, and study the influence of pion and quark masses on the equation of state at zero chemical potential. The obtained results are then compared with available lattice QCD data.