Violation of the holographic bulk viscosity bound

TL;DR

This paper demonstrates that in a specific strongly coupled gauge theory plasma, the effective hydrodynamic description violates a previously proposed lower bound on bulk viscosity when the curvature parameter is negative.

Contribution

It provides the first explicit example of a strongly coupled plasma where the holographic bulk viscosity bound is violated under certain geometric conditions.

Findings

Bulk viscosity exceeds the proposed bound for negative curvature parameter

Effective (1+1)-dimensional hydrodynamics captures the violation

Supports the possibility of bound violations in holographic models

Abstract

Motivated by gauge theory/string theory correspondence, a lower bound on the bulk viscosity of strongly coupled gauge theory plasma was proposed in arXiv:0708.3459. We consider strongly coupled N=4 supersymmetric Yang-Mills plasma compactified on a two-manifold of constant curvature beta. We show that the effective (1+1)-dimensional hydrodynamic description of the system is governed by the bulk viscosity violating the bound of arXiv:0708.3459, once beta<0.