Composite black holes in external fields

TL;DR

The paper develops exact multi-centered solutions for composite black holes in external fields within dilaton–Maxwell theories with an arbitrary number of U(1) gauge fields, extending Melvin, C and Ernst-type configurations. A central result is that, for extremal (BPS-like) configurations, the horizon area (and thus entropy) depends only on the conserved charges and remains invariant under external flux tubes and acceleration, even though the horizon can be distorted. The authors show the compositeness of extremal holes does not rely on supersymmetry and persists across diverse backgrounds, and they analyze pair creation via Euclidean instantons for both extremal and non-extremal cases. They also construct non-extremal static and accelerating solutions and discuss massless holes, stability considerations, and possible generalizations to higher dimensions and continuous charge distributions.

Abstract

The properties of composite black holes in the background of electric or magnetic flux tubes are analyzed, both when the black holes remain in static equilibrium and when they accelerate under a net external force. To this effect, we present a number of exact solutions (generalizing the Melvin, C and Ernst solutions) describing these configurations in a theory that admits composite black holes with an arbitrary number of constituents. The compositeness property is argued to be independent of supersymmetry. Even if, in general, the shape of the horizon is distorted by the fields, the dependence of the extreme black hole area on the charges is shown to remain unchanged by either the external fields or the acceleration. We also discuss pair creation of composite black holes. In particular, we extend a previous analysis of pair creation of massless holes. Finally, we give the generalization of our solutions to include non-extreme black holes.