Non-universal shear viscosity from Einstein gravity

TL;DR

This paper demonstrates how breaking rotational symmetry in Einstein gravity holography leads to non-universal shear viscosity ratios, expanding the understanding of anisotropic fluid dynamics in gauge/gravity duality.

Contribution

It introduces a method to break rotational symmetry spontaneously, showing that shear viscosities can deviate from universality in anisotropic holographic models.

Findings

Shear viscosities become non-universal when rotational symmetry is broken.

Explicit calculations in a p-wave superfluid confirm deviations from universality.

Critical behavior of shear viscosities near phase transitions is analyzed.

Abstract

A very famous result of gauge/gravity duality is the universality of the ratio of shear viscosity to entropy density in every field theory holographically dual to classical, two-derivative (Einstein) gravity. We present a way to obtain deviation form this universality by breaking the rotational symmetry spontaneously. In anisotropic fluids additional shear modes exist and their corresponding shear viscosities may be non-universal. We confirm this by explicitly calculating the shear viscosities in a transversely isotropic background, a p-wave superfluid, and study its critical behavior. This is a first decisive step towards further applications of gauge/gravity duality to physical systems.