Gravitons on Kerr as QFT on Curved Spacetime

Quantum field theory on curved spacetime is a framework to study quantum fields propagating on a classical and non-trivial spacetime. In this talk, I will discuss the case of quantum gravitational perturbations propagating around a rotating black hole. After having introduced the Teukolsky formalism to analyse classical perturbation around a Kerr black holes, I will show how to obtain field operators for metric perturbations. A constructive definition of gravitational quantum states and two-point functions will automatically follow. I will finally discuss the analysis of renormalized expectation values of (linear) gravitational observables on Kerr spacetime.