Cold Compressed Baryonic Matter with Hidden Local Symmetry and Holography

Abstract

I describe a novel phase structure of cold dense baryonic matter predicted in a hidden local symmetry approach anchored on gauge theory and in a holographic dual approach based on the Sakai-Sugimoto model of string theory. This new phase is populated with baryons with half-instanton quantum number in the gravity sector which is dual to halfskyrmion in gauge sector in which chiral symmetry is restored while light-quark hadrons are in the color-confined phase. It is suggested that such a phase that aries at a density above that of normal nuclear matter and below or at the chiral restoration point can have a drastic influence on the properties of hadrons at high density, in particular on shortdistance interactions between nucleons, e.g., multi-body forces at short distance and hadrons – in particular kaons – propagating in a dense medium. Potentially important consequences on the structure of compact stars will be predicted. 1. The Issue Baryonic matter near the nuclear matter density n0 ≈ 0.16 fm 3 is very well understood, thanks to many years of nuclear experimental and theoretical efforts, but there is a dearth of experimental information beyond n0. Unlike in high temperature where lattice QCD calculations come in tandem with experiments performed at relativistic heavy-ion colliders, there are no reliable theoretical tools available for dense matter for which lattice gauge calculation suffers from the notorious sign problem. Thus beyond n0, one knows very little of what’s going on. At asymptotically high density, perturbative QCD with weak coupling allows a clear-cut prediction, but the density required there is so high that it is hardly likely to be relevant to the physics of dense matter in terrestrial laboratories or in compact stars. A large number of model calculations are nonetheless available in the literature with a plethora of predictions for nucleon stars, quark stars etc., but the problem with these predictions is that constrained or aided neither by experiments nor by theory, it is difficult to assess the reliability of the calculations with wildly varying results at densities going beyond that of the nuclear matter. The prospect for the future, however, is pretty good, in particular experimentally. Indeed the forthcoming accelerators devoted to the physics of dense matter,