DOES THE NUCLEAR MEDIUM REACT AGAINST CHIRAL-SYMMETRY RESTORATION

It has recently been suggested that distortion effects due to rescattering of soft pions tend to reduce the sigma commutator per nucleon in heavy nuclei. We point out that the sigma commutator can always be calculated directly as a symmetry-breaking matrix element. The rescattering term should not be treated separately from other terms of similar magnitude. We illustrate this is in the linear sigma model where the full amplitude for soft-pion scattering from two nucleons is equivalent to the contribution to the commutator from sigma exchange between the nucleons. This leads instead to an enhancement of chiral symmetry restoration, although we expect it to be partly cancelled by omega exchange and the effects of correlations.