Shear Viscosity from Gauss-Bonnet Gravity with a Dilaton Coupling

TL;DR

This paper computes the shear viscosity to entropy density ratio in field theories with gravity duals involving Gauss-Bonnet gravity and a dilaton, revealing the dilaton's impact and potential slight violation of the known bound.

Contribution

It introduces the effect of a non-trivial dilaton in Gauss-Bonnet gravity on shear viscosity, extending previous bounds and constraints.

Findings

Dilaton modifies shear viscosity ratio.

Potential slight violation of the $4/25\pi$ bound.

Causal constraints influence the viscosity bound.

Abstract

We calculate the shear viscosity of field theories with gravity duals of Gauss-Bonnet gravity with a non-trivial dilaton using AdS/CFT. We find that the dilaton filed has a non-trivial contribution to the ratio of shear viscosity over entropy density and after imposing causal constraint for the boundary field theory, the new lower bound $4/25\pi$, obtained from pure Gauss-Bonnet gravity, may have a small violation.