Spectrum of density perturbations produced during inflation to leading order in a general slow-roll approximation

Abstract

The standard calculation of the spectrum of density perturbations produced during inflation assumes (i) parallel ton-1parallel to<1 and (ii) parallel todn/d ln kparallel to<parallel ton-1parallel to. Slow-roll predicts and observations require (i), but neither slow-roll nor observations require (ii). In this paper I derive formulas for the spectrum <tcal>P</tcal>, spectral index n, and running of the spectral index dn/d ln k, assuming only (i) and not (ii). I give a large class of observationally viable examples in which these general slow-roll formulas are accurate but the standard slow-roll formulas for the spectral index and running are incorrect.