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

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.

Comments: 18 pages; v4: added note and references; published version