E. Ruiz Arriola — Page 10

arXiv1994

Baryons in Effective Chiral Quark Models with Polarized Dirac Sea

We give a comprehensive review of concepts and numerical calculations for SU(2) and SU(3) baryonic systems which are considered as many body systems composed of three quarks coupled to a polarized Dirac sea by a Nambu--Jona-Lasinio like interaction. The general formalism as well as the construction and numerical solution of non-topological mean field solitons are exhibited. Systems with good spin/flavour/isospin/momentum quantum numbers are obtained by using the SU(2)/SU(3)-cranking and the pushing approach. The article contains also recent results for various extensions of the model, e.g. vector and axialvector couplings or the inclusion of scale invariance. Furthermore the relationship of this approach to topological models (Skyrme type) as well as to (valence-)quark-meson models (Gell-Mann--Levi chiral sigma model) is explained. (to be publ. in Rep.Prog.Phys.)

hep-ph↗

arXiv1993

Nucleon Properties and Restoration of Chiral Symmetry at Finite\nl Density and Temperature in an Effective Theory

Modifications of baryon properties due to the restoration of the chiral symmetry in an external hot and dense baryon medium are investigated in an effective chiral quark-meson theory. The nucleon arises as a soliton of the Gell-Mann - Lévi $\zs$-model, the parameters of which are chosen to be the medium-modified meson values evaluated within the Nambu - 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 densities and temperatures of the medium. Similar to the chiral phase transition line the critical curve in the $T-\zr$ plane for delocalization of the nucleon is non-monotonic and this feature is reflected in all nucleon properties. At medium densities of about $(2-3) \rnm$ the baryonic phase exists only at intermediate temperatures. For finite temperature and densities the nucleon form factors get strongly reduced at finite transfer momenta.

hep-ph↗