# Self-intersecting marginally outer trapped surfaces

## TL;DR

This paper confirms the merger of marginally outer trapped surfaces (MOTSs) in binary black hole mergers, introduces improved numerical methods for locating MOTSs, and demonstrates the formation of self-intersecting MOTSs post-merger, aiding gravitational wave analysis.

## Contribution

It provides numerical confirmation of MOTS mergers, details improved methods for locating MOTSs, and shows the formation of self-intersecting MOTSs after black hole mergers.

## Key findings

- Confirmed MOTS merger scenario numerically
- Demonstrated existence of self-intersecting MOTSs post-merger
- Enhanced numerical methods for locating MOTSs

## Abstract

We have shown previously that a merger of marginally outer trapped surfaces (MOTSs) occurs in a binary black hole merger and that there is a continuous sequence of MOTSs which connects the initial two black holes to the final one. In this paper, we confirm this scenario numerically and we detail further improvements in the numerical methods for locating MOTSs. With these improvements, we confirm the merger scenario and demonstrate the existence of self-intersecting MOTSs formed in the immediate aftermath of the merger. These results will allow us to track physical quantities across the non-linear merger process and to potentially infer properties of the merger from gravitational wave observations.