Stationary holographic plasma quenches and numerical methods for non-Killing horizons

TL;DR

This paper introduces a numerical method using harmonic Einstein equations to find stationary black holes without Killing horizons, illustrating their application in modeling non-equilibrium plasma flows via AdS/CFT correspondence.

Contribution

It presents a novel approach to compute stationary, non-Killing horizon black holes and demonstrates their relevance in holographic plasma dynamics with non-trivial spacetime geometries.

Findings

First explicit examples of stationary black holes without Killing horizons.

CFT stress tensor matches viscous hydrodynamics for slow variations.

Evidence of instability and possible turbulence in fast quenches.

Abstract

We explore use of the harmonic Einstein equations to numerically find stationary black holes where the problem is posed on an ingoing slice that extends into the interior of the black hole. Requiring no boundary conditions at the horizon beyond smoothness of the metric, this method may be applied for horizons that are not Killing. As a non-trivial illustration we find black holes which, via AdS-CFT, describe a time-independent CFT plasma flowing through a static spacetime which asymptotes to Minkowski in the flow's past and future, with a varying spatial geometry in-between. These are the first explicit examples of stationary black holes which do not have Killing horizons. When the CFT spacetime slowly varies, the CFT stress tensor derived from gravity is well described by viscous hydrodynamics. For fast variation it is not, and the solutions are stationary analogs of dynamical quenches, with the plasma being suddenly driven out of equilibrium. We find evidence these flows become unstable for sufficiently strong quenches, and speculate the instability may be turbulent.