Cosmic inflation in a landscape of heavy-fields
  Heavy isocurvature fields may have a strong influence on the low energy
dynamics of curvature perturbations during inflation, as long as the
inflationary trajectory becomes non-geodesic in the multi-field target space
(the landscape). If fields orthogonal to the inflationary trajectory are
sufficiently heavy, one expects a reliable effective field theory describing
the low energy dynamics of curvature perturbations, with self-interactions
determined by the shape of the inflationary trajectory. Previous work analyzing
the role of heavy-fields during inflation have mostly focused in the effects on
curvature perturbations due to a single heavy-field. In this article we extend
the results of these works by studying models of inflation in which curvature
perturbations interact with two heavy-fields. We show that the second
heavy-field (orthogonal to both tangent and normal directions of the
inflationary trajectory) may significantly affect the evolution of curvature
modes. We compute the effective field theory for the low energy curvature
perturbations obtained by integrating out the two heavy-fields and show that
the presence of the second heavy-field implies the existence of additional
self-interactions not accounted for in the single heavy-field case. We conclude
that future observations will be able to constrain the number of heavy fields
interacting with curvature perturbations.
