# Inside astronomically realistic black holes

## TL;DR

This paper explores the internal structure of realistic black holes, revealing that singularities are surfaces with diverging radiation energy density and that accretion leads to oscillatory collapse to a strong singular surface.

## Contribution

It provides a detailed analysis of the internal geometry of realistic black holes, including the effects of accretion and the nature of singular surfaces.

## Key findings

- Singularity in Schwarzschild black holes is a surface with diverging radiation density.
- Inside Kerr black holes, spacetime ends at the inner horizon due to mass inflation.
- Accreting black holes undergo oscillatory collapse to a strong, spacelike singular surface.

## Abstract

The singularity of a spherical (Schwarzschild) black hole is a surface, not a point. A freely-falling, non-rotating observer sees Hawking radiation with energy density diverging with radius as $\rho \propto r^{-6}$ near the Schwarzschild singular surface. Spacetime inside a rotating (Kerr) black hole terminates at the inner horizon because of the Poisson-Israel mass inflation instability. If the black hole is accreting, as all realistic black holes do, then generically inflation gives way to Belinski-Khalatnikov-Lifshitz oscillatory collapse to a strong, spacelike singular surface.