Gabriel Moreau "Backreaction of quantum scalar fields on de Sitter geometry: a non-perturbative renormalization group perspective"

Thursday 5 Sept 2019, 15:00 → 16:00 Europe/Rome

248 (Ed C)

We study the back-reaction of the infrared modes of an O(N) scalar theory in a classical de Sitter background. We use the nonperturbative renormalization group methods to extract analytically the flow of the Hubble constant as the gravitationally enhanced long wavelength modes are integrated out. For a massless theory, the interactions tend to renormalize negatively the Hubble constant, thus drawing energy from the classical gravitational field. This phenomenon saturates however, and unbounded loop corrections are screened by nonperturbative effects which stabilise the geometry. We also discuss the case of Goldstone modes, for a spontaneously broken symmetry, which do not contribute to the flow despite being strongly amplified.