S-wave ππ correlations in dense nuclear matter

Abstract

The s-wave correlated ππ strength distribution in cold nuclear matter is investigated. The inmedium single pions are renormalized by means of the usual p-wave couplings to nucleons and Δ's. Two groups of models for the ππ interaction are studied. The first one uses phenomenological models which reproduce the phase shifts but do not respect the soft-pion theorems. With increasing density a strong accumulation of strength in the subthreshold region is observed. Slightly above saturation density there even occurs an instability with respect to s-wave ππ pair condensation. These effects are strongly moderated or disappear altogether if constraints from chiral symmetry are built into the ππ interaction.