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

Abstract

The consortium NANOGrav discovered the isotropic gravitational wave background (GWB) with an amplitude of h ∼ 10 −15 and a frequency of f ∼ 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 ∼ 10 10 . The relic gravitational waves are similar to the gravitational waves with f ∼ 10 2 Hz discovered by LIGO in 2015, taking into account a decrease in frequency by a factor ∼ 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 . The SBMH mergers at Big Crunch should generate yet undiscovered GWB with a frequency of f ∼ 10 −(14−17) Hz.