Nucleon-Nucleon Correlations In Nuclear Matter

One of the current nuclear physics frontiers are discussed in this article, the properties of the nucleon-nucleon correlations in nuclear medium. First, the background in the nucleon-nucleon correlations research, research significance and current status are reviewed, as well as some nuclear many-body approaches, in particular the microscopic nuclear many-body theoretical framework of the Brueckner-Hartree-Fock (BHF) approach by including a microscopic three-body force. Next we laid a strong emphasis on our research results, including two parts.(1) The effect of tensor force on the properties of the nuclear matter have been investigated within the framework of the BHF approach. Besides, the BHF approach is extended by including a microscopic three-body force. Three-body force effect on the properties of the isospin asymmetric nuclear matter are carefully discussed under the gap and continuous choices.(2) The nucleon-nucleon correlations in the isospin symmetric, asymmetric nuclear matter and the finite nuclei systems are carefully investigated within the framework of the extended Brueckner-Hartree-Fock (EBHF) approach by adopting a microscopic three-body force, in particular the influence of the three-body force on them is investigated.The bare nucleon-nucleon interaction is a starting point of the Brueckner theory, which is powerful for the research of the nucleon-nucleon correlations in nuclear medium. The effect of tensor force on the asymmetric nuclear equation of state and the density dependence of nuclear symmetry energy have been investi-gated within the framework of the BHF approach in this paper. The tensor force manifests its effect via the3S1-3D1coupled channel,and the present results confirm the crucial role played by the tensor force in determining the isospin dependence of the equation of state of asymmetric nuclear matter and the densi-ty dependence of nuclear symmetry energy. The three-body force effects on the spectral functions and off-shell mass operator are also discussed in the symmetric and asymmetric nuclear matter within the framework of the EBHF approach plus a self-consistent microscopic three-body force, especially the density and isospin dependence for the quasi-particle peaks and Fermi-seas depletion. A stronger spectral peaks are observed for the proton than for the neutron in asymmetric case, as well as the spectral functions in the high energy region. This reflects separately the tensor and short-range correlations between the nucleons. The three-body force effects dependent sensitively the density and isospin asymme-try, which may sizably affect the nucleon-nucleon correlations. It shows that the three-body force effect turns out to be negligibly weak at low densities around and below the nuclear saturation density. At high densities, it is expected to in-duce stronger correlations in dense nuclear medium, which leads to a noticeable effect on the spectral functions and enhances both the depletion of the neutron and proton Fermi seas.On the basis of results above, the isospin dependence of the short-range cor-relations are investigated in the finite nucleus system by using the extended local density and isospin-asymmetry approximation. The calculations are consistent with not only the results of other different microscopic theoretic methods, but also the experimental data in J-lab. The results show that the EBHF approach plus a microscopic three-body force works well in the finite nucleus system.