Effect of inhomogeneities on the propagation of gravitational waves from binaries of compact objects

TL;DR

This paper investigates how inhomogeneities in the universe affect gravitational wave signals from distant sources, highlighting the importance of local structures on precision measurements in gravitational wave astronomy.

Contribution

It introduces a framework using Buchert's averaging to evaluate the impact of inhomogeneities on gravitational wave propagation and source parameter estimation.

Findings

Inhomogeneities significantly alter the redshift-distance relation.

Gravitational wave amplitude variations deviate from standard $ ext{Lambda}$CDM predictions.

Local structures impact the precision of gravitational wave source measurements.

Abstract

We consider the propagation of gravitational waves in the late time Universe with the presence of structure. Before detection, gravitational waves emitted from distant sources have to traverse through regions of spacetime which are far from smooth and homogeneous. We investigate the effect of inhomogeneities on the observables associated with the gravitational wave sources. In particular, we evaluate the impact of inhomogeneities on gravitational wave propagation by employing Buchert's framework of averaging. In context of a toy model within the above framework, it is first shown how the redshift versus distance relation gets affected through the averaging process. We then study the variation of the redshift dependent part of the observed gravitational wave amplitude for different combination of our model parameters. We show that the variation of the gravitational wave amplitude with respect to redshift can deviate significantly compared to that in the $\Lambda$CDM-model. Our result signifies the importance of local inhomogeneities on precision measurements of parameters of gravitational wave sources.