Finite baryon and isospin chemical potential in AdS/CFT with flavor

TL;DR

This paper explores the thermodynamics and phase structure of a strongly coupled gauge theory with baryon and isospin chemical potentials using holography, revealing symmetry breaking, spectral changes, and potential new condensed phases.

Contribution

It provides a detailed holographic analysis of phase diagrams, symmetry breaking, and spectral functions in a theory with baryon and isospin chemical potentials, including the discovery of a possible new condensed meson phase.

Findings

Symmetry in the phase diagram breaks at high densities.

A new low-energy excitation appears at large densities.

Instability of this excitation suggests a new condensed meson phase.

Abstract

We investigate the thermodynamics of a thermal field theory in presence of both a baryon and an isospin chemical potential. For this we consider a probe of several D7-branes embedded in the AdS-Schwarzschild black hole background. We determine the structure of the phase diagram and calculate the relevant thermodynamical quantities both in the canonical and in the grand canonical ensemble. We discuss how accidental symmetries present reflect themselves in the phase diagram: In the case of two flavors, for small densities, there is a rotational symmetry in the plane spanned by the baryon and isospin density which breaks down at large densities, leaving a Z_4-symmetry. Finally, we calculate vector mode spectral functions and determine their dependence on either the baryon or the isospin density. For large densities, a new excitation forms with energy below the known supersymmetric spectrum. Increasing the density further, this excitation becomes unstable. We speculate that this instability indicates a new phase of condensed mesons.