Non-analytical power law correction to the Einstein-Hilbert action: gravitational wave propagation

TL;DR

This paper investigates how a specific non-analytical f(R) gravity model alters gravitational wave properties, revealing non-transverse waves with different polarization and subluminal velocities, impacting GW detection tests.

Contribution

It provides an explicit solution for modified gravitational waves in a non-analytical f(R) model, highlighting their unique polarization and propagation features.

Findings

GWs are not transverse in this model.

Modified GWs have velocities much smaller than light.

The model's parameters critically influence GW speed.

Abstract

We analyze the features of the Minkowskian limit of a particular non-analytical f(R) model, whose Taylor expansion in the weak field limit does not hold, as far as gravitational waves (GWs) are concerned. We solve the corresponding Einstein equations and we find an explicit expression of the modified GWs as the sum of two terms, i.e. the standard one and a modified part. As a result, GWs in this model are not transverse, and their polarization is different from that of General Relativity. The velocity of the GW modified part depends crucially on the parameters characterizing the model, and it mostly results much smaller than the speed of light. Moreover, this investigation allows one to further test the viability of this particular f(R) gravity theory as far as interferometric observations of GWs are concerned.