Speaker: Dario Cannone

Abstract:

The theory of cosmological perturbations in standard single-field inflation can be interpreted as the effective field theory of fluctuations around a background that breaks time diffeomorphism invariance. A general consequence of this symmetry-breaking pattern is the production of a nearly scale-invariant, almost gaussian scalar perturbation, together with the two helicities of the gravitational waves. On the other hand, it might be possible that also spatial diffeomorphism invariance could be broken during inflation. The phenomenology of this possibility is extremely rich and still not fully explored, and can lead to unusual predictions for inflation, like non-conservation of curvature perturbations, masses for tensors and dynamical vectors.