Can the graviton have a large mass near black holes?

TL;DR

This paper proposes a gravity model where the graviton mass varies, being tiny in weak fields but significantly larger near black holes, leading to observable deviations in black hole signals.

Contribution

It introduces a model with environment-dependent graviton mass, predicting detectable effects on black hole ringdowns and potential gravitational wave echoes.

Findings

Deviations from general relativity near black hole horizons.

Possible gravitational wave echoes in late ringdown signals.

Enhanced graviton mass affects black hole quasi-normal modes.

Abstract

The mass of the graviton, if nonzero, is usually considered to be very small, e.g. of the Hubble scale, from several observational constraints. In this paper, we propose a gravity model where the graviton mass is very small in the usual weak gravity environments, below all the current graviton mass bounds, but becomes much larger in the strong gravity regime such as a black hole's vicinity. For black holes in this model, significant deviations from general relativity emerge very close to the black hole horizon and alter the black hole quasi-normal modes, which can be extracted from the ringdown waveform of black hole binary mergers. Also, the enhancement of the graviton mass near the horizon can result in echoes in the late time ringdown, which can be verified in the upcoming gravitational wave observations of higher sensitivity.