Seminarium Kosmologia i Fizyka Cząstek

Some well established concepts and methods of flat space QFT have to be reconsidered in curved space-time, in particular the question of observables. In cosmological context the concept of S-matrix makes little sense (at least for light fields) but yet there is no consensus on what good, gauge-invariant observables should be beyond tree level. I will present results on graviton loop corrections to the propagation of dynamical photons, and to the Coulomb force between point charges in de Sitter space-time. In the end I will discuss preliminary results on a method of addressing gauge dependence of quantum fluctuations in a single scalar inflation model.