Probing modified gravitational wave propagation with strongly lensed coalescing binaries

TL;DR

This paper explores how strongly lensed gravitational wave events from coalescing binaries can be used to test and constrain modifications to gravity at cosmological scales, especially through the parameter _0, without relying on electromagnetic counterparts.

Contribution

It demonstrates that quadruply lensed GW systems can constrain modified gravity parameters like _0 independently of prior assumptions on H_0, with current and future GW detectors.

Findings

Quadruply lensed GW events can localize sources to few galaxies.

Such systems can constrain the modified gravity parameter _0.

Third-generation detectors will significantly improve these constraints.

Abstract

It has been recently shown that quadruply lensed gravitational-wave (GW) events due to coalescing binaries can be localized to one or just a few galaxies, even in the absence of an electromagnetic counterpart. We discuss how this can be used to extract information on modified GW propagation, which is a crucial signature of modifications of gravity at cosmological scales. We show that, using quadruply lensed systems, it is possible to constrain the parameter $\Xi_0$ that characterizes modified GW propagation, without the need of imposing a prior on $H_0$. A LIGO/Virgo/Kagra network at target sensitivity might already get a significant measurement of $\Xi_0$, while a third generation GW detector such as the Einstein Telescope could reach a very interesting accuracy.