Relativistic Brueckner-Hartree-Fock calculations, with explicit intermediate negative energy states

Negative energy states are included explicitly in relativistic Brueckner-Hartree-Fock (RBHF) calculations by a medium-modified Gross spectator equation approach. An important advantage is the unambiguous determination of the Dirac and momentum structure of the RBHF self-energy. Applications to infinite symmetric nuclear matter are discussed. Qualitatively our results are close to conventional RBHF calculations. In detail, however, significant differences occur. They are related to the fact that a large part of the vector repulsion is generated dynamically by the explicit treatment of the negative energy states. The equation of state is stiffer and the momentum dependence of the self-energy components is stronger than found in a reference calculation without intermediate negative energy states. The density dependence of effective mean-field coupling constants is found to change considerably when Dirac-sea contributions are included.