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

Understand

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.