In this talk, divided into two parts, I discuss the origin and the evolution of the scalar bi-spectrum during inflation and preheating in single field inflationary models.
In the first part of the talk, after a brief outline of the Maldacena formalism to evaluate the scalar bi-spectrum, I shall present an efficient and accurate method to numerically compute the scalar bi-spectrum and the non-Gaussianity parameter fnl in single field inflationary models involving the canonical scalar field. Focusing on the equilateral limit, I shall illustrate the accuracy of the method by comparing the numerical results from the code with the spectral dependence of the bi-spectrum expected in power law inflation and the analytical results that have recently been obtained in the case of the Starobinsky model. As an immediate application, I shall discuss the utility of the code towards examining the power of the non-Gaussianity parameter fnl to discriminate between inflationary models that admit deviations from slow roll and lead to similar features in the scalar power spectrum.
The second part of the talk focuses on the contributions to the bi-spectrum during the epoch of preheating, which immediately follows inflation. I shall show that, in models involving a single scalar field wherein the potential behaves quadratically near the minimum, the contributions to the scalar bi-spectrum during preheating proves to be negligible.