Tests of weak equivalence principle with the gravitational wave signals in the LIGO-Virgo catalogue GWTC-1

TL;DR

This paper uses gravitational wave signals from LIGO-Virgo to test the weak equivalence principle over intergalactic distances, providing the most stringent constraints to date on potential violations.

Contribution

It introduces a novel method to constrain WEP violations using gravitational wave data from binary black hole mergers, achieving unprecedented sensitivity.

Findings

Constraint of |Δγ| < 10^{-15} at 90% confidence level

First application of GW data for WEP testing over intergalactic scales

Improves previous bounds from gamma-ray and radio burst observations

Abstract

The weak equivalence principle (WEP) is the cornerstone of gravitational theories. At the local scale, WEP has been tested to high accuracy by various experiments. On the intergalactic distance scale, WEP could be tested by comparing the arrival time of different messengers emitted from the same source. The gravitational time delay caused by massive galaxies is proportional to $\gamma+1$, where the parameter $\gamma$ is unity in general relativity. The values of $\gamma$ for different massless particles should be different if WEP is violated, i.e., $\Delta \gamma$ is used to indicate the deviation from WEP. So far, $|\Delta \gamma|$ has been constrained with gamma-ray bursts, fast radio bursts, etc. Here we report a new constraint of $|\Delta \gamma|$ by using the gravitational wave data of binary black hole coalescences in the LIGO-Virgo catalogue GWTC-1. The best constraints imply that $|\Delta \gamma| \lesssim 10^{-15}$ at 90 per cent confidence level.