One loop graviton corrections to dynamical photons in de Sitter
  We employ a recent, general gauge computation of the one loop graviton contribution to the vacuum polarization on de Sitter to solve for one loop corrections to the photon mode function. The vacuum polarization takes the form of a gauge independent, spin 2 contribution and a gauge dependent, spin 0 contribution. We show that the leading secular corrections derive entirely from the spin 2 contribution. 
D. Glavan, S. P. Miao, Tomislav Prokopec and R. P. Woodard
gr-qc astro-ph.CO hep-th