Relic gravitational waves and the cosmic accelerated expansion

TL;DR

This paper investigates how relic gravitational waves can reveal the Universe's expansion history, considering effects of early black holes, current acceleration, and thermodynamics, providing insights into cosmic evolution.

Contribution

It introduces a comprehensive analysis of relic gravitational wave spectra incorporating hypothetical eras and thermodynamic laws, advancing understanding of cosmic expansion phases.

Findings

Black hole-dominated era reduces the RGW spectrum significantly

Current accelerated expansion influences the RGW spectrum

Thermodynamic laws are consistent with the accelerated expansion

Abstract

The possibility of reconstructing the whole history of the scale factor of the Universe from the power spectrum of relic gravitational waves (RGWs) makes the study of these waves quite interesting. First, we explore the impact of a hypothetical era -right after reheating- dominated by mini black holes and radiation that may lower the spectrum several orders of magnitude. Next, we calculate the power spectrum of the RGWs taking into account the present stage of accelerated expansion and an hypothetical second dust era. Finally, we study the generalized second law of gravitational thermodynamics applied to the present era of accelerated expansion of the Universe.