Equation Of States And Properties Of Neutron Stars And Nucleon Superfluidity In Asymmetric Nuclear Matter

This thesis is contributed to the application of Relativistic Mean Field(RMF) theory,Brueckner-Hartree-Fock(BHF)approach and Bardeen-Cooper-Schriefer(BCS) theory in the investigation of equation of state(EOS)for asymmetric nuclear matter, the properties of neutron stars and nucleon superfluidity in asymmetric nuclear matter.The paper contains two parts.In the first part of this thesis,we investigate the EOS of asymmetric nuclear matter and properties of neutron stars in the framework of RMF theory.On the one hand,we introduce the strange meson fields(namely the scalar meson fieldσ^* and the vector meson fieldφ)to investigate the influences of hyperon-hyperon interaction on the properties of neutron stars.We find that the nonstrange mesons dominate essentially the global properties of dense hyperon matter.The weaker hyperon-hyperon interaction can lead to the stiffer EOS and larger predicted maximum mass of neutron star.On the other hand,we investigate the effects of scalar-isovector meson field on the properties of neutron stars.It was shown that the scalar-isovector meson field reduces the binding energy per baryon as well as increases the proton fraction and decreases the neutron fraction.The scalar-isovector meon field induces the splitting of the Dirac masses of baryons and the Dirac masses ofΣgets the biggest splitting.The RMF theory with the inclusion of the scalar-isovector field predicts the higher maximum mass of nucleonic star and the lower maximum mass of the neutron star with hyperons,this influence is slight.The most remarkable influence of scalarisovecor meson field on the global property of neutron star is the momentum of inertia which was enhanced obviously by the presence of scalar-isovector meson field.In the second part of this thesis,we investigate the isospin dependence of ³PF₂ nucleon superfluidity in asymmetric nuclear matter by using BHF approach and BCS theory.We get the solution of gap equations in ³PF₂ channel in a wide densities region within the BCS formwork.It means that the ³PF₂ nucleon superfluidity may occur in the core of neutron stars.We find that the peak values of neutron ³PF₂ pairing gaps increase and their locations shift to lower densities as the asymmetry rises.While the behavior of the dependence of proton ³PF₂ superfluidity is opposite. As the asymmetry rises,the peak values of proton ³PF₂ pairing gaps decrease and their locations shift to higher densities.We also find that the isospin-dependent AV18 NN interaction suppress the ³PF₂ pairing gaps markedly comparing with the isospin-independent AV14 NN interaction,and proton ³PF₂ paring can not occur in the case of AV18 NN interaction.