Causality of Holographic Hydrodynamics

TL;DR

This paper investigates how causality violations occur in holographic hydrodynamics within Gauss-Bonnet gravity, linking the coupling to conformal field theory properties and establishing constraints consistent with CFT analyses.

Contribution

It demonstrates causality violations in both truncated and exact holographic hydrodynamics theories, providing new constraints on the Gauss-Bonnet coupling from dual CFT considerations.

Findings

Causality is violated when the Gauss-Bonnet coupling exceeds a certain threshold.

Exact theory constraints are more restrictive than truncated theory.

Results align with previous CFT analyses by Hofman and Maldacena.

Abstract

We study causality violation in holographic hydrodynamics in the gauge theory/string theory correspondence, focussing on Gauss-Bonnet gravity. The value of the Gauss-Bonnet coupling is related to the difference between the central charges of the dual conformal gauge theory. We show that, when this difference is sufficiently large, causality is violated both in the second-order truncated theory of hydrodynamics, as well as in the exact theory. We find that the latter provides more stringent constraints, which match precisely those appearing in the CFT analysis of Hofman and Maldacena.