Modelling the final state from binary black-hole coalescences

TL;DR

This paper reviews semi-analytic models for predicting the final state of black holes after binary coalescence, focusing on spin and recoil velocity, highlighting their accuracy, limitations, and future prospects.

Contribution

It provides a comprehensive review of semi-analytic approaches for modeling black hole final states, comparing their strengths and weaknesses.

Findings

Semi-analytic models closely match numerical relativity results.

Current models have limitations in parameter space coverage.

Future improvements are likely to enhance predictive accuracy.

Abstract

Over the last few years enormous progress has been made in the numerical description of the inspiral and merger of binary black holes. A particular effort has gone into the modelling of the physical properties of the final black hole, namely its spin and recoil velocity, as these quantities have direct impact in astrophysics, cosmology and, of course, general relativity. As numerical-relativity calculations still remain computationally very expensive and cannot be used to investigate the complete space of possible parameters, semi-analytic approaches have been developed and shown to reproduce with very high precision the numerical results. I here collect and review these efforts, pointing out the relative strengths and weaknesses, and discuss which directions are more promising to further improve them.