HEP Therory Journal Club

Quantum Metric Perturbations and the Hubble Rate

Vincent Comeau

McGill

In this talk, I will discuss the effect of metric perturbations on the Hubble rate of an expanding universe, when the perturbations are treated as quantum fields. More particularly, I will argue that metric perturbations in a de Sitter background do not substantially modify the expansion rate of the background at first order. One could think that the massless modes of the metric perturbations would indeed change the expansion rate, in such a way that their correction would grow with time. I will show that, although such massless modes do exist, they do not contribute to the Hubble rate at first order.