Gravitational wave inference on a numerical-relativity simulation of a black hole merger beyond general relativity

TL;DR

This paper investigates the ability of gravitational wave inference methods to detect deviations from general relativity in black hole merger signals, using simulations based on a modified gravity theory called dynamical Chern-Simons gravity.

Contribution

It demonstrates that existing inference tools can identify deviations from general relativity in simulated waveforms from a modified gravity theory, highlighting the potential for future tests of gravity.

Findings

Waveform models based on general relativity cannot fully replicate modified gravity signals.

Morphology-independent analysis can faithfully reconstruct signals and detect deviations.

Template-based analysis may underperform in recovering beyond-GR waveforms at high SNRs.

Abstract

We apply common gravitational wave inference procedures on binary black hole merger waveforms beyond general relativity. We consider dynamical Chern-Simons gravity, a modified theory of gravity with origins in string theory and loop quantum gravity. This theory introduces an additional parameter $\ell$, corresponding to the length-scale below which beyond-general-relativity effects become important. We simulate data based on numerical relativity waveforms produced under an approximation to this theory, which differ from those of general relativity in the strongly nonlinear merger regime. We consider a system with parameters similar to GW150914 with different values of $\ell$ and signal-to-noise ratios. We perform two analyses of the simulated data. The first is a template-based analysis that uses waveforms derived under general relativity and allows us to identify degeneracies between the two waveform morphologies. The second is a morphology-independent analysis based on BayesWave that does not assume that the signal is consistent with general relativity. The BayesWave analysis faithfully reconstructs the simulated signals. However, waveform models derived under general relativity are unable to fully mimic the simulated modified-gravity signals and such a deviation would be identifiable with existing inference tools. Depending on the magnitude of the deviation, we find that the templated analysis can under perform the morphology-independent analysis in fully recovering simulated beyond-GR waveforms even for achievable signal-to-noise ratios $\gtrsim 20{-}30$.