Minimal cut-off vacuum state constraints from CMB bispectrum statistics

TL;DR

This paper translates observational CMB bispectrum bounds into constraints on a specific vacuum state modification model in single-field inflation, finding tight limits that challenge minimal cut-off scenarios especially with small sound speed.

Contribution

It provides the first translation of CMB bispectrum bounds into constraints on a scale-invariant vacuum state modification model within single-field inflation.

Findings

Bispectrum constraints impose strict upper bounds on the cut-off scale.

Most parameter domains are incompatible with power spectrum constraints.

Minimal cut-off vacuum modifications are highly constrained in models with small sound speed.

Abstract

In this short note we translate the best available observational bounds on the CMB bispectrum amplitudes into constraints on a specific scale-invariant New Physics Hypersurface (NPH) model of vacuum state modifications, as first proposed by Danielsson, in general models of single-field inflation. As compared to the power spectrum the bispectrum constraints are less ambiguous and provide an interesting upper bound on the cut-off scale in general models of single-field inflation with a small speed of sound. This upper bound is incompatible with the power spectrum constraint for most of the parameter domain, leaving very little room for minimal cut-off vacuum state modifications in general single-field models with a small speed of sound.