Detection of gravitational waves from black holes: Is there a window for alternative theories?

TL;DR

This paper explores whether current gravitational wave observations from black hole mergers can still accommodate alternative theories of gravity, given the uncertainties in black hole parameter measurements.

Contribution

It demonstrates that the current measurement uncertainties allow for certain deviations from Kerr spacetime, leaving room for alternative gravity theories.

Findings

Measurement uncertainties permit some deviations from Kerr spacetime.

Current data does not exclude alternative theories of gravity.

Black-hole ringing frequencies can be consistent with non-Kerr models.

Abstract

Recently LIGO and VIRGO collaborations reported about observation of gravitational-wave signal corresponding to the inspiral and merger of two black holes, resulting into formation of the final black hole. It was shown that the observations are consistent with the Einstein theory of gravity with high accuracy limited mainly by the statistical error. Angular momentum and mass of the final black hole were determined with rather large allowance of tens of percents. Here we shall show that this indeterminacy in the range of the black-hole parameters allows for some not negligible deformations of the Kerr spacetime leading to the same frequencies of black-hole ringing. This means that at the current precision of the experiment there remain some possibilities for alternative theories of gravity.