Magnetic fields from inflation: the transition to the radiation era
  We compute the contribution to the scalar metric perturbations from
large-scale magnetic fields which are generated during inflation. We show that
apart from the usual passive and compensated modes, the magnetic fields also
contribute to the constant mode from inflation. This is different from the
causal (post inflationary) generation of magnetic fields where such a mode is
absent and it might lead to significant, non-Gaussian CMB anisotropies.
