Property Of The Dielectric Function In Nuclear Matter

The nuclear property is one of the significant problem in theoretical nuclear physics. On one hand the nuclear matter is the proper configuration as in the nuclear level. And on the other hand it is a necessary background which should be extracted from the signal of the Quark gluon plasma(QGP), a new and most interesting matter that might be found in the heavy ion collision. The study of the nuclear property includes the Equation of state, the phase structure, the medium effect ect. This thesis focuses on the dielectric property at finite temperature and density in nuclear matter.The finite field theory is a fundamental theory established to study physical system in hot/dense environment, which contains tow totally different theoretical frames, one is the real-time formulism and the other is the imaginary-time formulism. This thesis introduces these two forms respectively and choose the first one for further discussion on the dielectric function in nuclear matter.Generally speaking, the discussion on the nuclear matter should base on a certain theoretical model. This thesis introduces the relativistic Quantum hadrodynamics I, II (QHD-1,11) model, which are widely accepted by most of the physicists. And the Feynman rules in the frame of real-time formulism at finite temperature for such models are also presented.The dielectric property is very important in the research of nuclear matter.In principle, it can discribe the essential difference between the filed in medium and in vacuum, which decides almost all the physical quantities concerning with the field strength.The p meson, because of its shorter life-time than that of the central ball in the heavy ion collision, is expected to carry the information of the ball and achieved more concentrations. This thesis is based on the QHD-II model and discusses the dielectric function excited by the three types of p meson polarizations at finite temperature. One trivial singularity is found on the dielectric function curve and two non-trivial extrema in the space-like and time-like regime respectively, in which the extremum in the space-like region reflects the Landau damping mechanism and the one in the time-like region is excited by the energy exchange of the collision between the meson and the nucleon or the meson and the meson.As far as the interactions between the p meson and the nucleon, only vector coupling is far from enough. Tensor coupling should be included in the interactive Lagrangian. This thesis discusses the dielectric function excited by pNN tensor coupling in nuclear matter and points out that to the iso-vector meson, the contribution form tensor coupling is much more larger than that of the vector coupling, in which the order of magnitude of the difference is especially amazing in the time-like region. Moreover, in the pNN tensor coupling, considering the polarization near the Fermi face of the nucleons, the dielectric function gives two unsymmetrical extrema at almost the same point in the time-like region. Withthe temperature rising, this unsymmetry becomes more and more obvious. Two different induced current mechanism are introduced to explain the extrema in the space-like and the time-like region respectively, especially the unsymmetrical structure of the extrema in the time-like region.