Drazen Glavan (University of Warsaw)
Photons are conformally coupled to gravity and therefore are produced due to cosmological expansion, while gravitons are experience explosive production due to the expansion of the primordial Universe. Since gravitons couple universally to all matter fields they can induce sizable effects to conformally coupled fields through loop corrections. I will present computations in two different gauges for the one-loop graviton corrections to photon vacuum polarization in de Sitter spacetime. This is used to quantum correct Maxwell equations, and I will present two cases, (i) correction to dynamical photons, and (ii) correction to the Coulomb force between two point charges. The corrections at late times exhibit (i) secular anti-screening of the point charge, and (ii) secular enhancement of the free photon electric field. Gauge dependence of the results will be discussed.