出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We discuss two models for describing the behavior of matter at large densities and intermediate
temperatures. In both models a softening of the equation of state takes place due to the appearance
of new degrees of freedom. The first is an hadronic model in which the softening is due to chiral
symmetry restoration, while in the second model the softening is associated with the formation of
clusters of quarks in the mixed phase. We show that both models allow a significant softening but,
in the hadronic model the bulk modulus is mainly dependent on the density, while in the mixedphase
model it also strongly depends on the temperature. We also show that the bulk modulus is
not vanishing in the mixed phase due to the presence of two conserved charges, the baryon and the
isospin one. Only in a small region of densities and temperatures the incompressibility becomes
extremely small. Finally we compare our results with recent analysis of heavy ion collisions at
intermediate energies.
