Abstract

In this talk I will review and discuss some recent developments on the study of inflation, regarding the possibility that heavy physics might have had an active role during inflation. For this, I will focus on two-field models of inflation characterized by a hierarchy of masses between curvature and isocurvature modes. I will show that when the hierarchy is large, a low energy effective field theory (EFT) exists in which only curvature modes participate in the dynamics of perturbations. In this EFT curvature perturbations exhibit a reduced speed of sound whenever the multi-field trajectory is subject to a sharp turn in target space. In particular, when turns are sharp and sudden, they are found to generate a variety of interesting observational effects, such as large features in the power spectrum and large non-Gaussianities. I will discuss the relevance of these results for a more refined understanding of inflation within fundamental theories.