Nonlinear chiralσmodel for nuclear matter

Abstract

In order to include pionic degrees of freedom in the description of nuclear many-body systems, the chiral {sigma} model in the nonlinear representation is investigated. The renormalizability of the model, which is obtained from the linear {sigma} model by a field transformation, is studied in the context of the equivalence theorem. It is shown that in any expansion scheme which is based on self-consistent mean scalar fields, the nonlinear {sigma} model should be considered as unrenormalizable (even if the {sigma} mass is kept finite), and new counterterms have to be introduced in each order. The resulting equation of state in the one-loop (Hartree) approximation is calculated, and the corresponding pion-nucleus optical potential is discussed. {copyright} {ital 1997} {ital The American Physical Society}