PROPERTIES OF N-ASTERISK-(1535) AT FINITE-DENSITY IN THE EXTENDED PARITY-DOUBLET MODELS

We improve so-called ''naive'' and ''mirror'' models for the positive and negative parity nucleons, N and N, by introducing non-linear term s allowed by chiral symmetry. Both models in this improvement reproduc e the observed nucleon axial charge in free space and reveal interesti ng density dependence of the axial charges for N and N, and the doubl et masses. A remarkable difference between the two models is found in the off-diagonal axial charge, g(ANN), which could appear either as s uppression or as enhancement of N --> pi N decay in the medium. (C) 1 998 Elsevier Science B.V.