HIGH-DENSITY MATTER IN THE CHIRAL SIGMA-MODEL

We present a field theoretical equation of state for nuclear matter an d neutron-rich matter in beta equilibrium using the chiral sigma model . The model includes an isoscalar vector field generated dynamically a nd reproduces the empirical values of the nuclear matter saturation de nsity and binding energy and the isospin symmetry coefficient for asym metric nuclear matter. The energy per nucleon of nuclear matter as pre dicted by our calculation is in very good agreement, up to about a den sity of 4n(s) (n(s) = nucleon number density for saturating nuclear ma tter), with the estimates inferred from heavy-ion collision data. An a strophysical application, relating to neutron star structure, is prese nted. An extension of the nuclear matter equation of state for finite temperatures (up to 15 MeV) is given, and the phase transition to (u, d, s) quark matter is discussed.