Cosmic in ation in a landscape of heavy-

Abstract

Heavy isocurvature elds may have a strong in uence on the low energy dynamics of curvature perturbations during in ation, as long as the in ationary trajectory becomes non-geodesic in the multi- eld target space (the landscape). If elds orthogonal to the in ationary trajectory are su ciently heavy, one expects a reliable e ective eld theory describing the low energy dynamics of curvature perturbations, with self-interactions determined by the shape of the in ationary trajectory. Previous work analyzing the role of heavy- elds during in ation have mostly focused in the e ects on curvature perturbations due to a single heavy- eld. In this article we extend the results of these works by studying models of in-

ation in which curvature perturbations interact with two heavy- elds. We show that the second heavy- eld (orthogonal to both tangent and normal directions of the in ationary trajectory) may signi cantly a ect the evolution of curvature modes. We compute the e ective eld theory for the low energy curvature perturbations obtained by integrating out the two heavy- elds and show that the presence of the second heavy- eld implies the existence of additional self-interactions not accounted for in the single heavy- eld case. We conclude that future observations will be able to constrain the number of heavy elds interacting with curvature perturbations.