On the effective field theory for quasi-single field inflation

Abstract

We study the effective field theory (EFT) description of the virtual particle effects in quasi-single field inflation, which unifies the previous results on large mass and large mixing cases. By using a horizon crossing approximation and matching with known limits, approximate expressions for the power spectrum and the spectral index are obtained. The error of the approximate solution is within 10% in dominate parts of the parameter space, which corresponds to less-than-0.1% error in the n(s)-r diagram. The quasi-single field corrections on the n(s)-r diagram are plotted for a few inflation models. Especially, the quasi-single field correction drives m(2)phi(2) inflation to the best fit region on the n(s)-r diagram, with an amount of equilateral non-Gaussianity which can be tested in future experiments.