Black Strings Ending on Horizons

TL;DR

This paper constructs an approximate gravitational solution describing a black string ending on a black brane horizon in AdS space, revealing the geometric structure and intersection of horizons.

Contribution

It introduces a derivative expansion method to model black strings in AdS, providing solutions up to second order and analyzing horizon intersections and black droplet configurations.

Findings

Black string shrinks to zero size at the black brane horizon.

Exact cone solution describes intersecting horizons at different temperatures.

The solution also models a thin, long black droplet.

Abstract

We construct an approximate static gravitational solution of the Einstein equations, with negative cosmological constant, describing a test black string stretching from the boundary of the Schwarzschild-AdS_5 black brane toward the horizon. The construction builds on a derivative expansion method, assuming that the black brane metric changes slowly along the black string direction. We provide a solution up to second order in derivatives and it implies, in particular, that the black string must shrink to zero size at the horizon of the black brane. In the near horizon region of the black brane, where the two horizons intersect, we provide an exact solution of a cone that describes two intersecting horizons at different temperatures. Moreover, we show that this solution equally describes a thin and long black droplet.