Universal relations of transport coefficients from holography

TL;DR

This paper demonstrates universal high-temperature relations for transport coefficients in a broad class of strongly coupled plasmas with gravity duals, highlighting bounds on sound speed, diffusion, conductivity, and viscosity.

Contribution

It establishes universal high-temperature bounds for multiple transport coefficients in holographic theories deformed by relevant operators.

Findings

Sound speed squared is bounded above by 1/3 at high temperatures.

Bounds on diffusion coefficient, conductivity, and bulk viscosity are discussed.

Universal relations hold across a wide class of holographic models.

Abstract

We show that there are universal high-temperature relations for transport coefficients of plasmas described by a wide class of field theories with gravity duals. These theories can be viewed as strongly coupled large-Nc conformal field theories deformed by one or more relevant operators. The transport coefficients we study are the speed of sound and bulk viscosity, as well as the conductivity, diffusion coefficient, and charge susceptibility of probe U(1) charges. We show that the sound bound v_s^2 <= 1/3 is satisfied at high temperatures in these theories and also discuss bounds on the diffusion coefficient, the conductivity and the bulk viscosity.