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Isospin dependence of nucleon effective mass in Dirac Brueckner-Hartree-Fock approach
The isospin dependence of the nucleon effective mass is investigated in the
framework of the Dirac Brueckner-Hartree-Fock (DBHF) approach. The definition
of nucleon scalar and vector effective masses in the relativistic approach is
clarified. Only the vector effective mass is the quantity related to the
empirical value extracted from the analysis in the nonrelatiistic shell and
optical potentials. In the relativistic mean field theory, where the nucleon
scalar and vector potentials are both energy independent, the neutron vector
potential is stronger than that of proton in the neutron rich nuclear matter,
which produces a smaller neutron vector effective mass than that of proton. It
is pointed out that the energy dependence of nucleon potentials has to be
considered in the analysis of the isospin dependence of the nucleon effective
mass. In the DBHF the neutron vector effective mass is larger than that of
proton once the energy dependence of nucleon potentials is considered. The
results are consistent with the analysis of phenomenological isospin dependent
optical potentials.Comment: 4 pages, 3 Postscript figure