The importance of slow-roll corrections during multi-field inflation

Abstract

We re-examine the importance of slow-roll corrections during the evolution of\ncosmological perturbations in models of multi-field inflation. We find that in\nmany instances the presence of light degrees of freedom leads to situations in\nwhich next to leading order slow-roll corrections become significant. Examples\nwhere we expect such corrections to be crucial include models in which modes\nexit the Hubble radius while the inflationary trajectory undergoes an abrupt\nturn in field space, or during a phase transition. We illustrate this with two\nexamples -- hybrid inflation and double quadratic inflation. Utilizing both\nanalytic estimates and full numerical results, we find that corrections can be\nas large as 20%. Our results have implications for many existing models in the\nliterature, as these corrections must be included to obtain accurate\nobservational predictions -- particularly given the level of accuracy expected\nfrom CMB experiments such as Planck\n