OPTIMIZED DELTA-EXPANSION FOR THE WALECKA MODEL

The optimized delta-expansion is used to study vacuum polarization eff ects in the Walecka model. The optimized delta-expansion is a nonpertu rbative approach for field theoretic models which combines the techniq ues of perturbation theory and the variational principle. Vacuum effec ts on self-energies and the energy density of nuclear matter are studi ed up to O(delta(2)). When exchange diagrams are neglected, the tradit ional relativistic Hartree approximation (RHA) results are exactly rep roduced and, using the same set of parameters that saturate nuclear ma tter in the RHA, a new stable, tightly bound state at high density is found.