Higher derivatives and power spectrum in effective single field
  inflation
  We study next-to-leading corrections to the effective action of the curvature
perturbation obtained by integrating out the coupled heavy isocurvature
perturbation. These corrections result from including higher order derivative
operators, weighted by the mass scale of the heavy physics, in the effective
theory expansion. We find that the correction terms are suppressed by the ratio
of the Hubble parameter to the heavy mass scale. The corresponding corrections
to the power spectrum of the curvature perturbation are presented for a simple
illustrative example.
