What Thermodynamics tells about QCD Plasma near Phase Transition
Due to a rapid change of the entropy density $s(T)$ across the critical temperature $T_c$ of the QCD phase transition, the pressure $P(T)$ and the energy density $e(T)$ above $T_c$ generally deviate from their Stefan-Boltzmann values. We shall demonstrate this both analytically and numerically for a general class of $s(T)$ consistent with thermodynamical constraints and make a qualitative comparison of the result with the lattice QCD data. Quantities related to $ds(T)/dT$ such as the specific heat and sound velocity are also discussed.