On the thermodynamics of hot hadronic matter

The equation of state of hot hadronic matter is obtained, by taking into account the contribution of the massive states, with the help of the resonance spectrum τ(m) ∼ m³ justified by the authors in previous papers. This equation of state is in agreement with that provided by the low-temperature expansion for the pion interacting gas. The formulas for the temperature dependence of the non-strange and strange quark condensates are derived by taking into account the contribution of the massive resonances. The critical temperature of the chiral symmetry restoration transition is established to be 190 MeV if only meson resonances are considered, and 180 MeV if both meson and baryon resonances are taken into account. The phase transition of chiral symmetry restoration is modelled by the restriction of the number of the effective degrees of freedom in the hadron phase to that of the microscopic degrees of freedom in the quark-gluon phase, through the corresponding truncation of the hadronic resonance spectrum, and the decrease of the effective hadron masses with temperature predicted by Brown and Rho. The results are in agreement with lattice gauge data and show a smooth crossover in the thermodynamic variables in a temperature range ∼ 50 MeV.