Hadronic chiral mean field models at extreme temperatures and densities

We study recently developed chiral mean field models under extreme conditio ns of temperature (T) and density (rho). The thermal vacuum phase transitio n (rho = 0 and high T), present in the Walecka model, also appears in some of the proposed models. A hadronic phase transition to a quark-gluon plasma phase (QGP) at rho not equal 0 is also shown in the T-rho phase diagram. F rom this diagram we see that, at rho = 0, the critical temperature T-c is n ot sensitive to the employed hadronic model whereas when rho increases and T decreases the hadronic-QGP two-phase transition becomes strongly model de pendent. Particular cases of the models at zero temperature and high densit y are discussed.