The near-horizon geometry of dilaton-axion black holes

TL;DR

This paper investigates the near-horizon geometry of dilaton-axion black holes by analyzing extreme rotating solutions and lifting the results to higher dimensions, revealing connections to Bertotti-Robinson-like geometries.

Contribution

It introduces a novel method to determine the near-horizon geometry of static dilaton-axion black holes by using extreme rotating solutions and dimensional lifting techniques.

Findings

Derived a Bertotti-Robinson-like near-horizon geometry for dilaton-axion black holes.

Connected four-dimensional solutions to six-dimensional vacuum gravity.

Provided insights into the geometry of extreme Kaluza-Klein black holes.

Abstract

Static black holes of dilaton-axion gravity become singular in the extreme limit, which prevents a direct determination of their near-horizon geometry. This is addressed by first taking the near-horizon limit of extreme rotating NUT-less black holes, and then going to the static limit. The resulting four-dimensional geometry may be lifted to a Bertotti-Robinson-like solution of six-dimensional vacuum gravity, which also gives the near-horizon geometry of extreme Kaluza-Klein black holes in five dimensions.