STRUCTURE OF THE VACUUM IN NUCLEAR-MATTER - A NONPERTURBATIVE APPROACH

We compute the vacuum polarization correction to the binding energy of nuclear matter in the Walecka model using a nonperturbative approach. We first study such a contribution as arising from a ground-state str ucture with baryon-antibaryon condensates. This yields the same result s as obtained through the relativistic Hartree approximation of summin g tadpole diagrams for the baryon propagator. Such a vacuum is then ge neralized to include quantum effects from meson fields through scalar- meson condensates which amounts to summing over a class of multiloop d iagrams. The method is applied to study properties of nuclear matter a nd leads to a softer equation of state giving a lower value of the inc ompressibility than would be reached without quantum effects. The dens ity-dependent effective sigma mass is also calculated including such v acuum polarization effects.