Curvature-Matter Coupling Effects on Axial Gravitational Waves

TL;DR

This paper studies how axial gravitational waves propagate in a flat FRW universe within $f(R,T)$ gravity, revealing their potential to induce cosmological rotation and memory effects due to curvature-matter coupling.

Contribution

It derives the field equations for axial perturbations in $f(R,T)$ gravity and explores their effects on matter and four-velocity, highlighting new implications for cosmological phenomena.

Findings

Perturbations influence matter and four-velocity.

Axial gravitational waves can produce cosmological rotation.

Discontinuities in wave profile lead to memory effects.

Abstract

In this paper, we investigate the propagation of axial gravitational waves in the background of the flat FRW universe in $f(R,T)$ theory. The field equations are obtained for unperturbed as well as axially perturbed FRW metric. These field equations are solved simultaneously to obtain the unknown perturbation parameters. We find that the assumed perturbations can affect matter as well as four-velocity. Moreover, ignoring the material perturbations we explicitly obtain an expression for four-velocity. It is concluded that axial gravitational waves in the curvature-matter coupling background can produce cosmological rotation or have memory effect if the wave profile has a discontinuity at the wavefront.