Resumming photon loops for inflationary gravity

A previous calculation of the one-loop photon contribution to the graviton self-energy on the de Sitter background is considered. We first show that there is no local obstacle to conservation, unlike the contribution from a loop of massless, minimally coupled scalars. This is correlated to the absence of an Eddington (R2) counterterm and to the vanishing of the stress tensor when the photon is integrated out in the presence of a constant graviton field. We also show that there is a secularly growing one-loop contribution to the electric components of the Weyl tensor for plane wave gravitons. Its coefficient agrees with that of the secular one-loop correction to the Newtonian potential, and both can be resummed using a variant of the renormalization group.