Numerical Relativity Investigation of the Effects of Gravitational Waves on the Inhomogeneity of the Universe

TL;DR

This study uses numerical relativity to explore how primordial gravitational waves influence the inhomogeneity of the universe, revealing an imprint on density perturbations that could serve as a future observational probe.

Contribution

It demonstrates that primordial tensor perturbations leave a detectable imprint on density inhomogeneities, despite not significantly affecting overdensity evolution.

Findings

Primordial tensor perturbations imprint on density distribution.

Tensor perturbations have minimal impact on scalar overdensity evolution.

Potential for future gravitational wave background detection through density inhomogeneity analysis.

Abstract

We numerically integrate the Einstein's equations for a spatially flat Friedmann-Lemaire-Robertson-Walker (FLRW) background spacetime with a spatial curvature perturbation and evolving primordial tensor perturbations using the Einstein Toolkit. We find that although the primordial tensor perturbation doesn't play an important role in the evolution of the overdensity produced by the scalar perturbation, there is an obvious imprint left by the primordial tensor perturbation on the distribution of the fractional density perturbation in the nonlinear region. This imprint may be a possible probe of a gravitational waves background in the future.