Anomalous Dimensions and Non-Gaussianity

TL;DR

This paper investigates how strongly coupled field theories influence inflationary models, revealing distinct non-Gaussian signatures in the bispectrum that serve as precision tests for such sectors.

Contribution

It provides a detailed analysis of the bispectrum scaling behavior near the squeezed limit in models coupled to strongly interacting theories, including CFTs and large-N deformations.

Findings

Bispectrum exhibits a range of shapes including equilateral, orthogonal, and local.

Scaling behavior near the squeezed limit is determined by operator dimensions.

Strongly coupled sectors can be tested via non-Gaussian signatures up to high energy scales.

Abstract

We analyze the signatures of inflationary models that are coupled to strongly interacting field theories, a basic class of multifield models also motivated by their role in providing dynamically small scales. Near the squeezed limit of the bispectrum, we find a simple scaling behavior determined by operator dimensions, which are constrained by the appropriate unitarity bounds. Specifically, we analyze two simple and calculable classes of examples: conformal field theories (CFTs), and large-N CFTs deformed by relevant time-dependent double-trace operators. Together these two classes of examples exhibit a wide range of scalings and shapes of the bispectrum, including nearly equilateral, orthogonal and local non-Gaussianity in different regimes. Along the way, we compare and contrast the shape and amplitude with previous results on weakly coupled fields coupled to inflation. This signature provides a precision test for strongly coupled sectors coupled to inflation via irrelevant operators suppressed by a high mass scale up to 1000 times the inflationary Hubble scale.