Gravitational wave background discovered by NANOGrav as evidence of a cyclic universe

TL;DR

This paper proposes that the gravitational wave background detected by NANOGrav is relic radiation from black hole mergers during a cyclic universe's Big Crunch, explaining observed features and predicting new signals.

Contribution

It introduces a novel model linking the GWB to black hole mergers in a cyclic universe, accounting for observed data and predicting a sharp amplitude decrease at certain frequencies.

Findings

The model explains the observed GWB spectrum well.

Predicts a sharp decrease in GWB amplitude at frequencies above 3.5×10^{-8} Hz.

Suggests existence of an undiscovered GWB at frequencies 10^{-(14-17)} Hz.

Abstract

The consortium NANOGrav discovered the isotropic gravitational wave background (GWB) with an amplitude of $h\sim 10^{-15}$ and a frequency of $f\sim 10^{-8}$ Hz using observations of millisecond pulsars. We hypothesize that the GWB is relic radiation left over from the merging stellar mass black holes (SBHs) during Big Crunch at $z\sim 10^{10}$. The relic gravitational waves are similar to the gravitational waves with $f\sim 10^2$ Hz discovered by LIGO in 2015, taking into account a decrease in frequency by a factor $\sim 10^{10}$ due to the expansion of the Universe. We take as a basis the observed spectrum of 139 SBHs, discovered by the LIGO observatory. Our model explains well all the observed features of the GWB. Unlike all other GWB models, our model predicts a sharp decrease in the GWB amplitude at frequencies $f>3.5*10^{-8}$ Hz, reflecting the deficit of SBHs with masses $<4M_\odot$. The SBMH mergers at Big Crunch should generate yet undiscovered GWB with a frequency of $f\sim 10^{-(14-17)}$ Hz.