A General Analytic Formula for the Spectral Index of the Density Perturbations produced during Inflation

Abstract

The standard calculation of the spectrum of density perturbations produced during inflation assumes that there is only one real dynamical degree of freedom during inflation. However, there is no reason to believe that this is actually the case. In this paper we derive general analytic formulae for the spectrum and spectral index of the density perturbations produced during inflation.Comment: 10 pages, more explanation and references added, version to be published in Progress of Theoretical Physic