Black Hole Mergers as the Fastest Photon Ring Scramblers

TL;DR

This paper shows that black hole mergers produce remnants with properties that maximize the instability of null geodesics, highlighting their exceptional efficiency as scramblers of information.

Contribution

It introduces a method to relate binary black hole mergers to an effective Kerr black hole, revealing a link between merger remnants and unstable null geodesics.

Findings

Merger remnants match the configuration with the highest null geodesic instability.

Black holes from mergers are the most efficient scramblers in nature.

The study uncovers a deep connection between black hole properties and null orbit instability.

Abstract

Black holes are the most efficient scramblers in nature. By mapping the instantaneous mass and angular momentum of two spinless black holes in a quasi-circular binary onto those of an effective Kerr black hole, we demonstrate that the final state of the merger remnant corresponds with remarkable accuracy to the configuration that renders null geodesics unstable at the highest possible rate. This suggests a deep connection between the properties of black holes resulting from binary mergers and their unstable null orbits.