One-loop graviton corrections to the curvature perturbation from inflation

We compute one-loop corrections to the power spectrum of the curvature perturbation in single-field slow-roll inflation arising from gravitons and inflaton interactions. The quantum corrections due to gravitons to the power spectrum of the inflaton field are computed around the time of horizon crossing and their effect on the curvature perturbation is obtained on superhorizon scales through the δN formalism. We point out that one-loop corrections from the tensor modes are of the same magnitude as those coming from scalar self-interactions; therefore they cannot be neglected in a self-consistent calculation.