Momentum, density, and isospin dependence of symmetric and asymmetric nuclear matter properties

Properties of symmetric and asymmetric nuclear matter have been investigated in the relativistic Dirac-Brueckner-Hartree-Fock approach based on projection techniques using the Bonn A potential. The momentum, density, and isospin dependence of the optical potentials and nucleon effective masses are studied. It turns out that the isovector optical potential depends sensitively on density and momentum, but is almost insensitive to the isospin asymmetry. Furthermore, the Dirac mass m_D^* and the nonrelativistic mass m_NR^* which parametrizes the energy dependence of the single particle spectrum, are both determined from relativistic Dirac-Brueckner-Hartree-Fock calculations. The nonrelativistic mass shows a characteristic peak structure at momenta slightly above the Fermi momentum k_F. The relativistic Dirac mass shows a proton-neutron mass splitting of m_D,n^*<m_D,p^* in isospin asymmetric nuclear matter. However, the nonrelativistic mass has a reversed mass splitting m_NR,n^*>m_NR,p^* which is in agreement with the results from nonrelativistic calculations.