Nucleon-nucleon Correlations In Nuclear Matter

Nucleon-nucleon (NN) correlations in nuclear medium are of great interest sincethey are closely related to many phenomena in nuclear physics and nuclear astro-physics. In this thesis, some important issues concerning NN correlations in nucle-ar medium have been explored and discussed within the framework of the extendedBrueckner-Hartree-Fock (EBHF) approach.The three-body force (TBF) efects on the of-shell behavior of the nucleon massoperators and spectral functions in symmetric and asymmetric nuclear matter havebeen investigated within the framework of the EBHF approach. In asymmetric nuclearmatter, it is shown that the proton spectral function has a more pronounced quasi-particle peak and a larger high-energy tail than the neutron one, which implies thatat a higher asymmetry the efect of the short-range correlations (SRC) induced bythe tensor component in NN interaction becomes stronger on protons as comparedwith that on neutrons. The TBF efect on the nucleon mass operators and spectralfunctions turns out to be negligibly weak at low densities around and below the nuclearsaturation density. At high densities well above the saturation density, the TBF mayafect noticeably the neutron and proton spectral functions. The TBF efect induces anextra SRC in dense nuclear medium, and shifts the peak locations in the neutron andproton spectral functions to higher energies.Based on the above microscopic results, the proton spectral function and itsisospin dependence in finite nuclei have been studied by using the local density ap-proximation and the local isospin-asymmetry approximation. The obtained results are shown to be not only consistent with the results predicted by diferent theoretic ap-proaches, but also compatible with the experimental data in JLab.The efects of tensor force on the equation of state (EOS) of asymmetric nuclearmatter and the density dependence of nuclear symmetry energy have also been investi-gated. The tensor force turns out to manifest its efect mainly via the3S13D1coupledchannel, and the present results confirm the crucial role played by the tensor force indetermining the density dependence of symmetry energy.