The shear viscosity of holographic superfluids

TL;DR

This paper investigates the shear viscosity to entropy density ratio in different holographic superfluids, revealing universal values in some cases and non-singular behavior at phase transitions.

Contribution

It provides new insights into shear viscosity behavior in p-wave and (p+ip)-wave holographic superfluids, extending previous universal results.

Findings

Shear viscosity ratio is universally 1/(4pi) for s-wave superfluids.

In p-wave superfluids, one shear viscosity coefficient remains universal.

Shear viscosity does not exhibit singular behavior at the superfluid phase transition.

Abstract

We study the ratio of the shear viscosity to the entropy density for various holographic superfluids. For the s-wave case, the ratio has the universal value 1/(4pi) as in various holographic models. For the p-wave case, there are two shear viscosity coefficients because of the anisotropic boundary spacetime, and one coefficient has the universal value. For the (p+ip)-wave case, the existing technique is not applicable since there is no tensor mode of metric perturbations which decouples from Yang-Mills perturbations. Our results indicate that the shear viscosity does not show a singular behavior at the critical point for holographic superfluids.