The Power Spectrum Of Gravitational Waves In Anisotropic Universe

TL;DR

This paper analyzes the power spectrum of primordial gravitational waves generated in anisotropic Bianchi type-I universes, highlighting differences between Einstein's and modified gravity frameworks, with modified gravity better preserving scale invariance.

Contribution

It investigates the gravitational wave power spectrum in anisotropic backgrounds within both Einstein and modified gravity theories, emphasizing the enhanced scale-invariance in modified gravity.

Findings

Modified gravity better fits physical constraints.

Scale-invariance more pronounced in modified gravity.

Anisotropic backgrounds influence gravitational wave spectra.

Abstract

One of the predictions from simple inflation models is a stochastic background of gravitational waves (or literally what is called the Primordial Gravitational Waves (\textbf{PGW})) with a nearly scale--invariant spectrum. In this work, we consider these waves arising from perturbing the Anisotropic background (Bianchi type--I) metric by focus on their power spectrums.The intended frameworks are the Einstein's and modified gravity frames. The investigations indicate that in the modified gravity context, the results have more ability to adapt to physical conditions or constraints. Especially, the scale--invariant character of the spectrum is much more pronounced in the modified framework.