The characteristic treatment of black holes

TL;DR

This paper presents a robust computational approach using characteristic techniques to analyze binary black holes, revealing new geometric features and improving waveform predictions for gravitational wave signals.

Contribution

It introduces the PITT NULL CODE for characteristic initial value problems and applies it to binary black holes, providing new insights into horizon geometry and waveform modeling.

Findings

Black holes undergo a toroidal phase before becoming spherical.

The conformal horizon structure aids in simulating exterior spacetime.

The method enhances understanding of post-merger gravitational waveforms.

Abstract

The characteristic initial value problem has been implemented as a robust computational algorithm (the PITT NULL CODE), with direct application to binary black holes. The event horizon can be analyzed by characteristic techniques as a stand-alone object using an analytic conformal model which gives new insight into the intrinsic geometry of binary black holes. When applied to a non-axisymmetric horizon, the model reveals substantially new features. Colliding black holes generically go through a toroidal phase before they become spherical. The conformal structure of the horizon supplies part of the data for a simulation of the exterior space-time and calculation of the post-merger waveforms from a binary black hole inspiral.