Gravitoelectromagnetic inflation and seeds of cosmic magnetic fields from geometrical Weyl-invariant scalar–tensor theory of gravity

Abstract

We investigate cosmological inflationary scenarios from a gravitoelectromagnetic theory. Our work is formulated in light of a recently introduced geometrical Weyl-invariant scalar–tensor theory of gravity, where the nature of both the electromagnetic potential and the inflaton field is attributed to the space–time geometry. We obtain a Harrison–Zeldovich power spectrum for quantum fluctuations of the inflaton field. In our model the electromagnetic fields also have a nearly scale-invariant power spectrum for a power-law inflation. We found that the seed magnetic fields have a nearly scale-invariant power spectrum and generate at the present time cosmic magnetic fields of the order ≲10−9 G, in good agreement with CMB observations.