Planck-Suppressed Operators

TL;DR

This paper investigates how Planck satellite constraints on primordial non-Gaussianity limit the interactions between the inflaton and hidden sector fields, requiring very high suppression scales for such couplings.

Contribution

It provides a detailed analysis of how Planck limits constrain Planck-suppressed operators coupling hidden sectors to the inflaton, establishing bounds on the suppression scale mbda.

Findings

Couplings to light hidden sector fields must be suppressed by mbda > 10^5 H for natural cubic interactions.

Nonlinear mixing can produce equilateral or orthogonal non-Gaussianity, requiring mbda > 10^2 H.

Planck data strongly constrains the strength of hidden sector interactions during inflation.

Abstract

We show that the recent Planck limits on primordial non-Gaussianity impose strong constraints on light hidden sector fields coupled to the inflaton via operators suppressed by a high mass scale \Lambda. We study a simple effective field theory in which a hidden sector field is coupled to a shift-symmetric inflaton via arbitrary operators up to dimension five. Self-interactions in the hidden sector lead to non-Gaussianity in the curvature perturbations. To be consistent with the Planck limit on local non-Gaussianity, the coupling to any hidden sector with light fields and natural cubic couplings must be suppressed by a very high scale \Lambda > 10^5 H. Even if the hidden sector has Gaussian correlations, nonlinearities in the mixing with the inflaton still lead to non-Gaussian curvature perturbations. In this case, the non-Gaussianity is of the equilateral or orthogonal type, and the Planck data requires \Lambda > 10^2 H.