The Impact of the Polyakov Effective Potential on the Deconfinement Transition of QCD Matter

In this study, we analyzethe deconfinement phase transition in quantum chromodynamics (QCD) by combining the hadron resonance gas (HRG) model at low temperatures with the Polyakov-Nambu-Juna-Lacinio (PNJL) model near the deconfinement region considering two flavors of quarks. By using a switching function (SF), a connection between the HRG and quark-gluon plasma (QGP) phases via the SF ensures the continuity of the thermodynamic variables and, consequently, a smooth crossover from the HRG phase to the QGP phase. The PNJL model represents an extension of the Nambu-Juna-Lacinio (NJL) model by incorporating both quark chiral dynamics and the Polyakov loop, thus enabling a more realistic description of the QGP phase and its thermodynamic properties. In this analysis, emphasis is placed on the investigation of several important thermodynamic quantities—such as pressure, energy density, specific heat density, and the square of speed of sound—as functions of temperature at zero chemical potential. We focus on the role of the Polyakov effective potential near the deconfinement region and its impact on the thermodynamic behavior of the strongly interacting matter. The obtained results are compared with the available lattice quantum chromodynamics (LQCD) data, demonstrating that the combined HRG–PNJL framework provides a consistent description of the QCD crossover and reproduces key thermodynamic features around the transition temperature.