SPIN POLARIZATION IN HIGH DENSITY QUARK MATTER

We investigate the occurrence of a ferromagnetic phase transition in high density hadronic matter (e.g., in the interior of a neutron star). This could be induced by a four-fermion interaction analogous to the one which is responsible for chiral symmetry breaking in the Nambu–Jona-Lasinio model, to which it is related through a Fierz transformation. Flavor SU(2) and flavor SU(3) quark matter are considered. A second-order phase transition is predicted at densities about 5 times the normal nuclear matter density. It is also found that in flavor SU(3) quark matter, a first-order transition from the so-called 2 flavor super-conducting phase to the ferromagnetic phase arises. The color-flavor-locked phase may be completely hidden by the FP.

PION CONDENSATION BASED ON A RELATIVISTIC DESCRIPTION OF PARTICLE-HOLE AND DELTA-HOLE EXCITATIONS

The critical density of neutral pion condensation is reinvestigated based on the relativistic framework and compared with nonrelativistic results. The particle-hole and delta-hole polarizations of the pion selfenergy are calculated in the relativistic way by using a new set of Landau–Migdal parameters derived from recent experimental data. It is concluded that the use of relativistic particle-hole and delta-hole excitations for the pion selfenergy increases the critical density, but still leads to condensation for densities from two to three times the normal nuclear matter density within the random phase approximation.

Binding Energy of Neutron Star Matter

The energy per particle of neutron star matter is calculated using reaction matrix elements deduced from Reid's potential. These are parameterized so that the calculation is presented in a simple form. A maximum concentration of nearly 9% protons is found at about twice normal nuclear matter density.