Higher order nonlinear parameters with Planck constraints

Abstract

We investigate how higher-order nonlinear parameters affect lower-order ones through loop effects. We calculate the loop corrections up to two loops and explicitly show that the tree contribution is stable against loop terms in most cases. We argue that, nevertheless, observational constraints on nonlinear parameters such as f_NL and τ_NL can also give a limit even for higher-order ones due to the loop contribution. We discuss these issues for both single-source and multisource cases.