Modified gravity and the black hole mass gap
Abstract
We pioneer the black hole mass gap as a powerful new tool for constraining modified gravity theories. These theories predict fifth forces that alter the structure and evolution of populationIII stars, exacerbating the pairinstability. This results in the formation of lighter astrophysical black holes and lowers both the upper and lower edges of the mass gap. These effects are explored using detailed numerical simulations to derive quantitative predictions that can be used as theoretical inputs for Bayesian data analysis. We discuss detection strategies in light of current and upcoming data as well as complications that may arise due to environmental screening. To demonstrate the constraining power of the mass gap, we present a novel test of the strong equivalence principle where we apply our results to an analysis of the first ten LIGO/Virgo binary black hole merger events to obtain a 7% bound on the relative difference between the gravitational constant experienced by baryonic matter, and that experienced by black holes, ∆ G /G . The recent GW190521 event resulting from two black holes with masses in the canonical mass gap can be explained by modified gravity if the event originated from an unscreened galaxy where the strength of gravity is either enhanced or reduced by ∼30 % relative to its strength in the Solar System.
 Publication:

Physical Review D
 Pub Date:
 December 2020
 DOI:
 10.1103/PhysRevD.102.124018
 arXiv:
 arXiv:2009.10716
 Bibcode:
 2020PhRvD.102l4018S
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  High Energy Astrophysical Phenomena;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory
 EPrint:
 Updated to reflect published version, minor additions