Horizon Pretracking

TL;DR

Horizon pretracking is a novel method for early detection and analysis of apparent horizons in merging black hole simulations, enabling more efficient and predictive modeling of black hole mergers.

Contribution

The paper introduces horizon pretracking, a new technique for tracking modified constant expansion surfaces to predict the formation of common apparent horizons in black hole simulations.

Findings

Efficient early detection of apparent horizons.

Ability to predict horizon properties before formation.

Potential to improve simulation boundary and gauge conditions.

Abstract

We introduce horizon pretracking as a method for analysing numerically generated spacetimes of merging black holes. Pretracking consists of following certain modified constant expansion surfaces during a simulation before a common apparent horizon has formed. The tracked surfaces exist at all times, and are defined so as to include the common apparent horizon if it exists. The method provides a way for finding this common apparent horizon in an efficient and reliable manner at the earliest possible time. We can distinguish inner and outer horizons by examining the distortion of the surface. Properties of the pretracking surface such as its expansion, location, shape, area, and angular momentum can also be used to predict when a common apparent horizon will appear, and its characteristics. The latter could also be used to feed back into the simulation by adapting e.g. boundary or gauge conditions even before the common apparent horizon has formed.