The phenomenology of trapped inflation

Trapped inflation is a mechanism in which particle production from the moving inflaton is the main source of friction in the inflaton equation of motion. The produced fields source inflaton perturbations, which dominate over the vacuum ones. We review the computation of the perturbations performed in the original work and in a successive analysis that makes use of the effective field theory (EFT) of inflation. We verify the validity of several results obtained in these works, but we show that the final expression for the power spectrum is affected by one invalid approximation. This approximation also affects the computation of the bispectrum. We show that, once this approximation is replaced by an exact computation, the different schemes used in the literature to compute the perturbations at second order lead to different results for the bispectrum. ar X iv :1 60 3. 08 02 1v 3 [ as tr oph .C O ] 7 D ec 2 01 6