Chiral symmetry and strangeness content in nuclear physics parametrized by a medium dependent bag constant

Non-perturbative QCD vacuum effects at finite density are parametrized by means of a bag constant B. It is extracted from a Nambu-Jona-Lasinio model with two or three flavors. The parameter B is used in an effective bag-like model of baryons to study the nuclear phenomenology. We examine the nucleon structure and the thermodynamical properties of symmetric nuclear matter, particular attention is paid to the symmetry energy and to the eventual phase transition to deconfined quark matter. An alternative sketch of the binding mechanism of symmetric nuclear matter emerges within this approach. It is also found that the inclusion of strangeness content in B is crucial for an appropriate description. (C) 2003 Published by Elsevier Science B.V.