NUCLEAR SCHWINGER-DYSON FORMALISM APPLIED TO FINITE BARYON DENSITY .2. NUMERICAL-CALCULATIONS AND MEDIUM EFFECTS OF MESON SELF-ENERGIES

Numerical results based on coupled equations of the nuclear Schwinger- Dyson (NSD) without and with the sigma-omega meson mixing under a bare -vertex approximation are shown. Comparisons between NSD and tradition al methods such as the mean field theory (MFT) or Hartree-Fock (HF) ar e made. It is shown that higher order effects beyond HF are important because they modify. properties of mesons in the nuclear medium. Becau se of a large negative of a scalar meson self-energy, the scalar meson in NSD without the mixing works more attractively than in HF. From a comparison between NSD without and with the meson mixing, mixing ring energies are extracted and it is shown that the mixing works repulsive ly and the ring energy with the mixing cancels partially the ring ener gy without the mixing. Nevertheless, NSD leads to smaller couplings th an MFT or HF, i.e., g(s) = 8.714, g(v) = 10.678 in the nonmixed calcul ation, and g(s) = 7.590, g(v) = 8.462 in the mixed calculation. The NS D with the meson mixing gives a smaller incompressibility k = 386 MeV than the other models. It is also shown that MFT or HF approximation i s able to simulate the saturation curve of the binding energy of NSD w ithout the mixing ff their couplings are refitted so as to reproduce t he experimental saturation point, however, MFT or HF cannot simulate t he saturation curve of NSD with the meson mixing even if their couplin g constants are adjusted.