Gravitational wave memory produced by cosmic background radiation

Abstract

It is well known that energy fluxes will produce gravitational wave memory. The gravitational wave memory produced by background including cosmic microwave background (CMB), cosmic neutrino background (CνB), and gravitational wave background is investigated in this work. We construct a theory relating the gravitational wave memory strength to the energy flux of a stochastic background. We find that the resulted gravitational wave memory behaves as a constantly varying metric tensor. Such a varying metric tensor will introduce a quadrupole structure to the universe expansion. The gravitational wave memory due to the CMB is too small to be detected. But the gravitational wave memory due to the CνB and the gravitational wave background is marginally detectable. Interestingly, such detection can be used to estimate the neutrino masses and the properties of the gravitational wave background.