Primordial non-gaussianities in single field inflation

Abstract

We calculate the three-point function for primordial scalar fluctuations in a single field inflationary scenario where the scalar field Lagrangian is a completely general function of the field and its first derivative. We obtain an explicit expression for the three-point correlation function in a self-consistent approximation scheme where the expansion rate varies slowly, analogous to the slow-roll limit in standard, single-field inflation. The three-point function can be written in terms of the familiar slow-roll parameters and three new parameters which measure the non-trivial kinetic structure of the scalar field, the departure of the sound speed from the speed of light, and the rate of change of the sound speed.

26 pages, uses iopart.cls. Updated to match version published in JCAP