# The Marolf-Ori singularity inside fast spinning black holes

## TL;DR

This paper numerically investigates the Marolf-Ori singularity inside fast spinning black holes, demonstrating shock wave formation and quantifying its sharpening effect for scalar and gravitational perturbations.

## Contribution

It provides the first detailed numerical analysis of the Marolf-Ori singularity inside spinning black holes, including scalar and gravitational perturbations.

## Key findings

- Shock wave singularity occurs at the inner horizon.
- Scalar field and Weyl scalars show order unity changes.
- Shock sharpening rate matches theoretical expectations.

## Abstract

The effective shock wave singularity at the outgoing leg of the inner horizon of a linearly perturbed fast spinning black hole is studied numerically for either scalar field, or vacuum, gravitational perturbations. We demonstrate the occurrence of the Marolf-Ori singularity, including changes of order unity in the scalar field $\phi$ for the scalar field model, and in the Weyl scalars $\psi_0$ and $\psi_4$ (rescaled appropriately by the horizon function $\Delta$) and the Kretschmann curvature scalar $K$ for the vacuum, gravitational perturbations model for both null and timelike geodesic observers. We quantify the shock sharpening effect and show that in all cases its rate agrees with expectations.