The impact of higher derivative corrections to General Relativity on black hole mergers

TL;DR

This paper investigates how higher derivative corrections to General Relativity, specifically Einsteinian cubic gravity, influence black hole merger dynamics in the extreme mass ratio limit, focusing on changes in merger duration and area increase.

Contribution

It extends the extreme mass ratio approach to higher derivative gravity theories, analyzing the impact on black hole merger characteristics within Einsteinian cubic gravity.

Findings

Merger duration varies with the coupling parameter.

The relative area increment is affected by higher derivative corrections.

The approach provides insights into gravitational modifications during mergers.

Abstract

The merging of two black holes is a notoriously difficult process to describe exactly. Nevertheless, the hindrances posed by gravity's nonlinearity can be circumvented by focusing on the strict extreme mass ratio limit, in which one of the black holes is infinitely larger than the other. Such an approach has been developed by Emparan and Mart\'inez and applied within General Relativity to investigate the time evolution of event horizons melding, using nothing but elementary concepts in gravitational physics and simple integrations of geodesics. We apply this strategy to study black hole mergers in higher derivative gravity, in order to assess how the defining characteristics of the fusion process change as the gravitational theory is modified. We adopt the case of Einsteinian cubic gravity for concreteness, and determine how the mergers' duration and the relative area increment change as the theory's single coupling parameter is varied.