QCD Vacuum Changes in Nuclei

Abstract

In this talk, I discuss how the changes in the QCD vacuum induced by increasing nuclear matter density affect nuclear properties under normal as well as extreme conditions. The quark condensate which is the order parameter for the mode in which chiral symmetry is manifested is expected to change as matter density or temperature is changed. The topics discussed are ``BR scaling," its connection to the structure of nuclei in Landau's Fermi liquid theory and a variety of consequences on such nuclear properties as effective nucleon mass, nuclear gyromagnetic ratios, $g_A^\star$, axial-charge transitions in nuclei and on the fluctuations of nuclear matter into the strange-flavor direction as observed in heavy-ion collisions. I will also present a simple explanation of the recent dilepton data in the CERN-CERES heavy-ion experiments involving densities greater than that of nuclear matter and of the Indiana results on the longitudinally polarized proton scattering from heavy nuclei, evidencing dropping vector-meson masses in medium which can be interpreted as signaling an aspect of chiral symmetry restoration in dense medium. The test of BR scaling provides a bridge between the physics of extreme conditions (e.g. relativistic heavy-ion collisions) and the physics of normal conditions which has conventional descriptions, thereby setting the stage for formulating many-body theory for nuclear matter starting from an effective chiral Lagrangian.