On the apparent horizon in fluid-gravity duality

TL;DR

This paper develops a covariant computational method to locate apparent horizons in fluid-gravity duality, revealing a unique horizon expressible in terms of fluid variables and proposing a connection to entropy currents in black hole spacetimes.

Contribution

It introduces a second-order covariant framework for apparent horizons in fluid-gravity duality, suggesting a universal horizon structure and linking it to entropy currents.

Findings

Existence of a unique covariant apparent horizon up to second order

Explicit construction of an entropy current from the apparent horizon

Potential for preferred horizon foliation in near-equilibrium regimes

Abstract

This article develops a computational framework for determining the location of boundary-covariant apparent horizons in the geometry of conformal fluid-gravity duality in arbitrary dimensions. In particular, it is shown up to second order and conjectured to hold to all orders in the gradient expansion that there is a unique apparent horizon which is covariantly expressible in terms of fluid velocity, temperature and boundary metric. This leads to the first explicit example of an entropy current defined by an apparent horizon and opens the possibility that in the near-equilibrium regime there is preferred foliation of apparent horizons for black holes in asymptotically-AdS spacetimes.