Curvature spectra and nongaussianities in the roulette inflation model

Using the gradient expansion method of Rigopoulos, Shellard and van Tent which treats cosmological perturbations as gradients on top of a homogeneous and isotropic FRW background, we study the production of nongaussianities in the roulette model of inflation. Investigating a number of trajectories within this two-field model of inflation, we find that while the superhorizon influence of the isocurvature modes on the curvature bispectrum produces nonzero contribution to fNL, the effect is negligible next to the standard inflationary prediction |fNL| ∼ ns-1. This is the case in both the squeezed and equilateral configurations of the bispectrum, although the former is slightly larger in the trajectories under consideration.