Quasi-single field inflation and non-Gaussianities

Abstract

In quasi-single field inflation models, massive isocurvature modes,that are coupled to the inflaton and have mass of order the Hubbleparameter, can have nontrivial impacts on density perturbations,especially non-Gaussianities. We study a simple example of quasi-single field inflation in terms of turning inflaton trajectory. Large bispectra with aone-parameter family of novel shapes arise, lying between thewell-known local and equilateral shape. The trispectra can also bevery large and its magnitude tNL can be much larger than fNL2.