Asymmetric Nuclear Matter Equation Of State And Kaon Condensation In Neutron Star Matter

In this thesis, the status of neutron star and some important nuclear many-body approaches are introduced. The asymmetric cold and hot nuclear matter equation of state, the kaon condensation inβ-stable neutron star matter are discussed, in particular the influence of the three-body force and the hyperon degree of freedom on it are investigated.We explore the effects of a microscopic nuclear three body force on the threshold baryon density for kaon condensation in chemical equilibrium neutron star matter and on the composition of the kaon condensed phase in the framework of the Brueckner-Hartree-Fock approach. Our results show that the nuclear three-body force affects strongly the high-density behavior of nuclear symmetry energy and consequently reduces considerably the critical density for kaon condensation provided that the proton strangeness content is not very large. The dependence of the threshold density on the symmetry energy becomes weaker as the proton strangeness content increases. The kaon condensed phase of neutron star matter turns out to be proton-rich instead of neutron-rich. The three-body force has an important influence on the composition of the kaon condensed phase. Inclusion of the three-body force contribution in the nuclear symmetry energy results in a significant reduction of the proton and kaon fractions in the kaon condensed phase which is more proton-rich in the case of no three-body force.We investigate the composition and the equation of state of the kaon condensed phase in neutrino-free and neutrino-trapped star matter within the framework of the Brueckner-Hartree-Fock approach with three-body forces. We find that neutrino trapping shifts the onset density of kaon condensation to a larger baryon density and reduces considerably the kaon abundance. As a consequence, when kaons are allowed, the equation of state of neutrino-trapped star matter becomes stiffer than the one of neutrino free matter. The effects of different three-body forces are compared and discussed. Neutrino trapping turns out to weaken the role played by the symmetry energy in determining the composition of stellar matter and thus reduces the difference between the results obtained by using different three-body forces.By using the new experimental data of AA potential, we have performed a full calculation for strange hadronic matter with different strangeness contents as well as its consequences on the global properties of neutron star matter in relativistic mean field model. We find that the new weak hyperon-hyperon interaction makes the equations of state much stiffer as compared to the result of the previous strong hyperon-hyperon interaction, and even stiffer than the result without consideration of hyperon-hyperon interaction. This new hyperon-hyperon interaction results in a maximum mass of 1.75M_?, about 0.2 - 0.5M_? larger than the previous prediction with the presence of hypreons. After examining carefully the onset densities of kaon condensation we find that this new weak version of hyperon-hyperon interaction favors the occurrence of kaons comparing with the strong one.