NUCLEON PROPERTIES AND RESTORATION OF CHIRAL-SYMMETRY AT FINITE-DENSITY AND TEMPERATURE IN AN EFFECTIVE THEORY

Modifications of baryon properties due to the restoration of the chira l symmetry in an external hot and dense baryon medium are investigated in an effective chiral quark-meson theory. The nucleon arises as a so liton of the Gell-Mann-Levi sigma-model, the parameters of which are c hosen to be the medium-modified meson values evaluated within the Namb u-Jona-Lasinio model. The nucleon properties are obtained by means of variational projection techniques. The nucleon form factors as well as the nucleon-delta transition form factors are evaluated for various d ensities and temperatures of the medium. Similar to the chiral phase t ransition line the critical curve in the T - rho plane for delocalizat ion of the nucleon is non-monotonic and this feature is reflected in a ll nucleon properties. At medium densities of about (2-3)rho(nm) the b aryonic phase exists only at intermediate temperatures. For finite tem perature and densities the nucleon form factors get strongly reduced a t finite transfer momenta.