Numerical Calculation of Inflationary Non-Gaussianities

Abstract

In this thesis the numerical calculation of non-Gaussianity from inflation is discussed. Despite a strong interest in non-Gaussianity from inflation models in recent years, not much attention has been devoted to its numerical computation. Calculating the inflationary bispectrum in an efficient and accurate manner will become more important as observational constraints on primordial non-Gaussianity continue to increase. Despite this, attention given to numerically calculating the primordial bispectrum has been relatively low. The approach presented here differs from previous approaches in that the Hubble Slow-Roll (HSR) parameters are treated as the fundamental parameters. This allows one to calculate the bispectra for a variety of scales and shapes in the out-of-slow-roll regime and makes the calculation ideally suited for Monte-Carlo sampling of the bispectrum. The work is further extended to include potentials with features and non- canonical kinetic terms, where the standard squeezed limit consistency re- lation is demonstrated even for models which produce large f NL in the equilateral limit. The method presented here is also independent of the standard field redefinition used in analytic calculations, removing the need for delicate cancellations in the super-horizon limit used in other numerical methods.