Stringy holography at finite density

TL;DR

This paper explores an exactly solvable string theory model in a black brane background with gauge flux, revealing finite-density effects and dual fluid behaviors in a holographic setting.

Contribution

It constructs explicit string vertex operators for gauge and stress tensors and analyzes their two-point functions at finite density and temperature.

Findings

Low-energy excitations follow hydrodynamics at zero charge density.

System behaves as two noninteracting fluids at high density.

Identifies shear and sound mode excitations in each fluid.

Abstract

We consider an exactly solvable worldsheet string theory in the background of a black brane with a gauge field flux. Holographically, such a system can be interpreted as a field theory with finite number of degrees of freedom at finite temperature and density. This is to be contrasted with more conventional holographic models which involve gravity in the bulk and possess infinite number of degrees of freedom and mean field critical exponents. We construct closed string vertex operators which holographically represent the U(1) gauge field and the stress energy tensor and compute their two-point functions. At finite temperature and vanishing charge density the low energy excitations are described by hydrodynamics. As the density is raised, the system behaves like a sum of two noninteracting fluids. We find low-energy excitations in the shear and sound channels of each fluid.