The Merger of Small and Large Black Holes

TL;DR

This paper investigates the complex interactions of merging black holes through simulations, focusing on the behavior of their marginally outer trapped surfaces and the implications for black hole coalescence.

Contribution

It explores the relationship between theoretical MOTS properties and numerical simulations of small and large black hole mergers, revealing potential coalescence scenarios.

Findings

MOTSs of merging black holes can penetrate each other.

Theoretical implications suggest possible coalescence of black holes.

Simulations show a small black hole halfway penetrates a large one.

Abstract

We present simulations of binary black holes mergers in which, after the common outer horizon has formed, the marginally outer trapped surfaces (MOTSs) corresponding to the individual black holes continue to approach and eventually penetrate each other. This has very interesting consequences according to recent results in the theory of MOTSs. Uniqueness and stability theorems imply that two MOTSs which touch with a common outer normal must be identical. This suggests a possible dramatic consequence of the collision between a small and large black hole. If the penetration were to continue to completion then the two MOTSs would have to coalesce, by some combination of the small one growing and the big one shrinking. Here we explore the relationship between theory and numerical simulations, in which a small black hole has halfway penetrated a large one.