Effect of curvature squared corrections in AdS on the viscosity of the dual gauge theory

TL;DR

This paper investigates how curvature squared corrections in AdS space influence the shear viscosity of the dual gauge theory, revealing potential violations of the viscosity bound in certain finite N scenarios.

Contribution

It demonstrates the impact of R^2 corrections on shear viscosity in AdS/CFT, providing explicit examples where the viscosity bound is violated.

Findings

R^2 corrections modify shear viscosity in AdS/CFT

The viscosity-to-entropy ratio can fall below 1/(4π)

Finite N effects can violate the conjectured bound

Abstract

We use the real-time finite-temperature AdS/CFT correspondence to compute the effect of general R^2 corrections to the gravitational action in AdS space on the shear viscosity of the dual gauge theory. The R^2 terms in AdS_5 are determined by the central charges of the CFT. We present an example of a four-dimensional gauge theory in which the conjectured lower bound of 1/(4\pi) on the viscosity-to-entropy ratio is violated for finite N.