Nuclear Structure Probes Of Asymmetric Nuclear Matter And The Structure Of Neutron Stars

The equation of state（EOS） of asymmetric nuclear matter is a long-standing, fundamental problem in nuclear physics. It plays an important role also in astrophysics and new physics beyond standard model. To date, the EOS of symmetric nuclear matter is relatively well constrained from the study of finite nuclei and heavy ion collision,while that of asymmetric nuclear matter, especially its isospin dependent part, namely the symmetry energy, is poorly understood, even around saturation density ρ0.In this thesis, within the framework of phenomenological mean field theory（e.g.Skyrme-Hartree-Fock（SHF） and Relativistic mean field（RMF） theory）, we have obtained very strong constraints on the EOS of asymmetric nuclear matter at subsaturation densities from analysis of different ground state properties and giant resonance observables in finite nuclei. Besides, by employing the standard and extended SHF model, we systematically investigate the properties of neutron stars, and demonstrate the important role played by the symmetry energy.This thesis is organized in four chapters. In the first chapter we have given a brief introduction to the significance and status of research on the EOS of asymmetric nuclear matter, as well as the motivation of our work.In the second chapter, using the correlation analysis method based on the standard SHF model, we demonstrate that the neutron skin thickness ?rnpof heavy nuclei is uniquely fixed by the symmetry energy density slope L（ρ） at a subsaturation cross density ρ_c≈ 0.11 fm^-3rather than at saturation density ρ0, while the binding energy difference ?E between a heavy isotope pair is essentially determined by the magnitude of the symmetry energy E_sym（ρ） at the same ρ_c. Furthermore, from these two probes,we extract simultaneously constraints on E_sym（ρ_c） and L（ρ_c）. We also determine a globally optimized parameter set of Skyrme force denoted as MSL1. Based on MSL1 we predict the magnitude and density slope of the symmetry energy at saturation density using the constraints on E_sym（ρ_c） and L（ρ_c）. Moreover, the core-crust transition density and neutron skin thickness of208 Pb and132Xe are also discussed.In the third chapter, the correlations between some giant resonance observables and the EOS of asymmetric nuclear matter are studied. Firstly, through the RPA and constrained Hartree-Fock（CHF） calculations, we show that the constrained energy of isoscalar giant monopole resonance（ISGMR） is an excellent experimental probe of incompressibility coefficient of symmetric nuclear matter. For isovector giant dipole resonance（IVGDR）, we focus on the investigation of the electric dipole polarizabilityαD, a good probe of the density dependence of the symmetry energy. We demonstrate that the electric dipole polarizibility αDin208Pb is sensitive to both E_sym（ρ_c） and L（ρ_c）.Using the experimental data of αDin208Pb from RCNP and the recent accurate constraint of E_sym（ρ_c） from the binding energy difference of heavy isotope pairs, we extract a constraint on L（ρ_c）, which is in very good agreement with the constraint we extracted from neutron skin thickness. Furthermore, analyses within macroscopic hydrodynamical and droplet model, and RPA calculations using a number of non-relativistic and relativistic mean-field models conclude that the electric dipole polarizability αDin208Pb can be determined uniquely by the magnitude of the E_sym（ρr） or almost equivalently the EPNM（ρr） at subsaturation densities ρr≈ ρ0/3, and there exists a strong linear correlation between 1/αDand E_sym（ρr） or EPNM（ρr）. Thus we can obtain very stringent constraints on E_sym（ρ） and EPNM（ρ） around ρ0/3 from experimental data of αD.Besides, through RPA calculations using a number of SHF parameter sets, we extract isoscalar and isovector effective mass from isoscalar giant quadruple resonance and isovector giant dipole resonance, respectively. And the isospin splitting of nucleon effective mass is also discussed.In the last chapter, within the framework of standard SHF model, we study the correlation between neutron star structure and the EOS of asymmetric nuclear matter.We find that the core-crust transition density is determined by the density slope of the symmetry energy, the radius of a 1.4M⊙neutron star is strong correlated with L（ρ0）and the maximum mass is very sensitive to the symmetry energy at high densities,thus related to many isovector characteristic quantities at saturation density. At last, to eliminate unphysical instabilities in asymmetric nuclear matter at high densities in SHF model, we extend the standard Skyrme interaction by taking account of the momentum dependence of many-body force and construct three new extended Skyrme interactions by fitting properties of finite nuclei and nuclear matter, which would be very useful in study of neutron stars.