Large slow-roll corrections to the bispectrum of noncanonical inflation
Ribeiro, Raquel H (DAMTP, University of Cambridge)

Nongaussian statistics are a powerful discriminant between inflationary models, particularly those with noncanonical kinetic terms. Focusing on theories where the Lagrangian is an arbitrary Lorentz-invariant function of a scalar field and its first derivatives, I report the calculation of the observable three-point function. I obtain quantitative estimates of their magnitude in DBI and power-law k-inflation. In the DBI case these results enable an estimate corrections from the shape of the potential and the warp factor: these can be of order several tens of percent. I also identify a new bispectrum shape available at next-order, which is similar to a shape encountered in Galileon models. If fNL is sufficiently large this shape may be independently detectable provided a new template for CMB analysis is devised.