A Near Horizon Extreme Binary Black Hole Geometry

TL;DR

This paper introduces a novel exact solution in General Relativity describing the near horizon geometry of a binary system of maximally spinning, uncharged black holes held in equilibrium, revealing new insights into their structure and entropy.

Contribution

It presents the first non-supersymmetric, asymptotically flat near horizon geometry for an extreme binary black hole system with two identical Kerr black holes.

Findings

Describes a unique, explicit solution for the near horizon region of the binary system.

Shows the system has finite entropy and a fixed inter-black hole distance.

Reveals a zero-distance limit where the binary merges into a single NHEK black hole.

Abstract

A new solution of four-dimensional vacuum General Relativity is presented. It describes the near horizon region of the extreme (maximally spinning) binary black hole system with two identical extreme Kerr black holes held in equilibrium by a massless strut. This is the first example of a non-supersymmetric, asymptotically flat near horizon extreme binary black hole geometry of two uncharged black holes. The black holes are co-rotating, and the solution is uniquely specified by the mass. The binary extreme system has finite entropy. The distance between the black holes is fixed, but there is a zero-distance limit where the objects collapse into one. This limiting geometry corresponds to the near horizon extreme Kerr (NHEK) black hole.