Nucleon Momentum Distribution In Asymmetric Nuclear Matter And Neutrino Emissivities Inside Of Neutron Stars

To determine reliably the properties of isospin asymmetric nuclear matter is a challenge in nuclear physics and nuclear astrophysics. The nucleon momentum distribution in nuclear matter is one of the most important properties of nuclear matter. Besides, the nucleon momentum distribution measures the short range correlations(SRCs) in nuclear many-body system, which are currently much concerned by experiments. First, in the present thesis the nucleon momentum distribution in asymmetric nuclear matter has been investigated within the framework of the Extended Brueckner Hartree Fock(BHF) approach. On the other hand, neutron stars are ideal natural laboratories and their structure and cooling properties are important for constraining the equation of state(Eo S)of asymmetric nuclear matter at high densities. Second, in the present thesis the neutrino emissivities of neutron stars have been explored and discussed. In addition, the phenomenological effective nucleon-nucleon interactions have been widely used in nuclear physics and nuclear astrophysics due to their simple physical interpretation and formalism. However, the validity of these interactions is not guaranteed at high densities and large isospin asymmetries, so it is necessary to constrain phenomenological effective interactions according to the predictions of microscopic many-body approaches. In the present thesis a new Skyrme effective interaction is obtained based on the microscopic BHF approach.First, the nucleon momentum distributions and their isospin-asymmetry dependence in asymmetric nuclear matter have been investigated and predicted within the framework of the Extended BHF approach. Especially, the effects of three-body forces(TBFs) and the neutron-proton tensor correlations have been stressed in the thesis. It is shown that the TBF effect is negligibly small at low densities around and below the saturation density, whereas it enhances strongly the depletion of nucleons below Fermi surface at high densities, due to the extra SRCs induced by the TBF. The isospin dependence of the nucleon momentum distributions turns out to be mainly determined by the neutron-proton tensorcorrelations. The contribution from the neutron-proton correlations is estimated to account almost 90% of the total SRCs, which is in agreement with the experimental results at JLab. Second, the neutrino emissivities in neutron star matter and neutron stars are studied within the framework of the BHF approach. It is shown that the TBF may lead to a strong decrease of the critical density of the Direct Urca(DU) process. However, the TBF effect on the total neutrino luminosities of neutron stars is much less strong than that expected previously. For instance, only 50% increase is gained for neutron stars with the mass of 1.8M⊙by inclusion of the TBF. In addition, the model-dependence of the neutrino emissivities is explored by adopting the Skyrme interactions. The model-dependence of the DU process turns out to come mainly from the nucleon effective mass and that of the Modified Urca process mainly from the symmetry energy and the nucleon effective mass. It is also shown that the model-dependence of the total neutrino luminosities of neutron stars is mainly decided by the symmetry energy,the nucleon effective mass as well as the Eo S of neutron star matter. Finally, a set of Skyrme parameters is obtained by fitting the results from the BHF approach and the contributions from the two-body force and the TBF are distinguished during the fitting procedure.