Entropy Current and Fluid-Gravity Duality in Gauss-Bonnet theory

TL;DR

This paper explores the duality between horizon entropy currents and boundary entropy currents in Gauss-Bonnet gravity, revealing that higher-order derivatives influence the fluid description of entropy in holographic duals.

Contribution

It constructs a boundary entropy current from the horizon current in Gauss-Bonnet gravity and analyzes its dependence on derivative order and mapping choices.

Findings

Gauss-Bonnet terms do not affect entropy at first order in derivatives.

At second order, the boundary entropy current depends on the horizon-boundary mapping.

The boundary entropy current may not always be expressible purely in fluid variables.

Abstract

Working within the approximation of small amplitude expansion, recently an entropy current has been constructed on the horizons of dynamical black hole solution in any higher derivative theory of gravity. In this note, we have dualized this horizon entropy current to a boundary entropy current in an asymptotically AdS black hole metric with a dual description in terms of dynamical fluids living on the AdS boundary. This boundary entropy current is constructed using a set of mapping functions relating each point on the horizon to a point on the boundary. We have applied our construction to black holes in Einstein-Gauss-Bonnet theory. We have seen that up to the first order in derivative expansion, Gauss-Bonnet terms do not add any extra corrections to fluid entropy as expected. However, at the second order in derivative expansion, the boundary current will non-trivially depend on how we choose our horizon to boundary map, which need not be expressible entirely in terms of fluid variables. So generically, the boundary entropy current generated by dualizing the horizon current will not admit a fluid dynamical description.