Holographic phase transitions at finite baryon density

TL;DR

This paper uses holographic methods to analyze phase transitions in a strongly coupled gauge theory with finite baryon density, revealing a critical point and potential new phases.

Contribution

It extends holographic studies of meson melting to finite baryon density, identifying a critical point and thermodynamic instabilities in the phase diagram.

Findings

Identified a line of first order phase transitions ending at a critical point.

Discovered a region with negative slope of chemical potential versus density, indicating instability.

Suggested the possibility of a new phase emerging in the unstable region.

Abstract

We use holographic techniques to study SU(Nc) super Yang-Mills theory coupled to Nf << Nc flavours of fundamental matter at finite temperature and baryon density. We focus on four dimensions, for which the dual description consists of Nf D7-branes in the background of Nc black D3-branes, but our results apply in other dimensions as well. A non-zero chemical potential mu or baryon number density n is introduced via a nonvanishing worldvolume gauge field on the D7-branes. Ref. [1] identified a first order phase transition at zero density associated with `melting' of the mesons. This extends to a line of phase transitions for small n, which terminates at a critical point at finite n. Investigation of the D7-branes' thermodynamics reveals that (d mu / dn)_T <0 in a small region of the phase diagram, indicating an instability. We comment on a possible new phase which may appear in this region.