Gravitational waves induced by massless vector fields with non-minimal coupling to gravity

Published 28 Nov 2016 in gr-qc and hep-th | (1611.09032v1)

Abstract: In this paper, we calculate the contribution of the late time mode of a massless vector field to the power spectrum of the primordial gravitational wave using retarded Green's propagator. We consider a non-trivial coupling between gravity and the vector field. We find that the correction is scale-invariant and of order $\frac{H^{4}{M_P^4}$.} The non-minimal coupling leads to a dependence of $\frac{H^{2}{M^2}$,} which can amplify the correlation function up to the level of $\frac{H^{2}{M^2_P}$.}