Extremal Black Holes in Strong Magnetic Fields: Near-Horizon Geometries and Meissner Effect

TL;DR

This paper explores the near-horizon geometries of extremal black holes in strong magnetic fields, revealing enhanced symmetries and their relation to the magnetic field expulsion known as the Meissner effect.

Contribution

It demonstrates the universality of near-horizon geometries for extremal black holes in strong magnetic fields and links this to the physical Meissner effect.

Findings

Near-horizon geometries exhibit enhanced symmetry.

Strong magnetic fields are expelled from extremal black holes.

Universality of limiting spacetimes for different solutions.

Abstract

For extremal black holes, one can construct simpler, limiting spacetimes that describe the geometry near degenerate horizons. Since these spacetimes are known to have enhanced symmetry, the limiting objects coincide for different solutions. We show that this occurs for strongly magnetised Kerr-Newman solution, and how this is related to physical Meissner effect of expulsion of magnetic fields from extremal black holes.