Modeling the QCD equation of state throughout the thermal deconfining phase transition from hadronic matter to a Quark–Gluon Plasma

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 square of the speed of sound, and study the influence of pion and quark masses on the equation of state (EOS). This analysis provides a better understanding of the interplay between particle properties and the thermodynamic properties of the system, helping to provide a more comprehensive and accurate picture of the thermal behavior of hadronic matter at zero chemical potential, including its response to changes in temperature and energy. This is essential for interpreting heavy-ion collision results and simulating early-universe conditions. Our analysis results are systematically compared with available lattice QCD data, providing valuable insights and allowing us to assess the accuracy of the model and its ability to describe strongly interacting matter at high temperatures.