Black holes in an Effective Field Theory extension of GR

TL;DR

This paper constructs and analyzes black hole solutions within an effective field theory extension of General Relativity, revealing unique properties like non-symmetric geometries and nonzero tidal Love numbers, with implications for gravitational-wave and electromagnetic observations.

Contribution

It develops black hole solutions in an EFT extension of GR, including rotating cases without $ ext{Z}_2$ symmetry, and studies their stability, tidal responses, and quasinormal modes.

Findings

First example of geometries without $ ext{Z}_2$-symmetry in such theories

Linearized fluctuations obey second-order equations despite higher-order operators

Nonzero tidal Love numbers and computed quasinormal modes

Abstract

Effective field theory methods suggest that some rather-general extensions of General Relativity include, or are mimicked by, certain higher-order curvature corrections, with coupling constants expected to be small but otherwise arbitrary. Thus, the tantalizing prospect to test the fundamental nature of gravity with gravitational-wave observations, in a systematic way, emerges naturally. Here, we build black hole solutions in such a framework and study their main properties. Once rotation is included, we find the first purely gravitational example of geometries without $\mathbb{Z}_2$-symmetry. Despite the higher-order operators of the theory, we show that linearized fluctuations of such geometries obey second-order differential equations. We find nonzero tidal Love numbers. We study and compute the quasinormal modes of such geometries. These results are of interest to gravitational-wave science but also potentially relevant for electromagnetic observations of the galactic center or $X$-ray binaries.