Bounds on Generic High-Energy Physics Modifications to the Primordial Power Spectrum from Back-Reaction on the Metric

TL;DR

This paper investigates how high-energy physics modifications to the primordial power spectrum are constrained by back-reaction effects on the metric, revealing bounds that limit their observational detectability.

Contribution

It highlights the importance of back-reaction effects in constraining the parameters of high-energy modifications to inflationary perturbations.

Findings

Back-reaction imposes bounds on parameters H/M.

Some modifications may be unobservable due to back-reaction constraints.

The approach refines previous models by including metric back-reaction effects.

Abstract

Modifications to the primordial power spectrum of inflationary density perturbations have been studied recently using a boundary effective field theory approach. In the approximation of a fluctuating quantum field on a fixed background, the generic effect of new physics is encoded in parameters of order H/M. Here, we point out that the back-reaction on the metric can be neglected only when these parameters obey certain bounds that may put them beyond the reach of observation.