Signatures of very high energy physics in the squeezed limit of the bispectrum (violation of Maldacena's condition)

TL;DR

This paper explores how high-energy modifications to inflationary physics, such as altered dispersion relations or initial states, can produce distinctive signatures in the squeezed limit of the primordial bispectrum, potentially revealing new physics.

Contribution

It provides a detailed analysis of the effects of high-energy modifications on the bispectrum's squeezed limit, highlighting observable signatures that differ from standard inflation models.

Findings

Enhanced non-Gaussianities in the squeezed limit due to high-energy effects

Non-local shape features distinguish these scenarios from standard models

Signatures vary with the scale of new physics, offering potential observational bounds

Abstract

We investigate the signatures in the squeezed limit of the primordial scalar bispectrum due to modifications of the standard theory at high energy. In particular, we consider the cases of modified dispersion relations and/or modified initial quantum state (both in the Boundary Effective Field Theory and in the New Physics Hyper-Surface formulations). Using the in-in formalism we study in details the squeezed limit of the contributions to the bispectrum from all possible cubic couplings in the effective theory of single-field inflation. We find general features such as enhancements and/or non-local shape of the non-Gaussianities, which are relevant, for example, for measurements of the halo bias and which distinguish these scenarios from the standard one (with Bunch-Davies vacuum as initial state and standard kinetic terms). We find that the signatures change according to the magnitude of the scale of new physics, and therefore several pieces of information regarding high energy physics could be obtained in case of detection of these signals, especially bounds on the scales of new physics.