Covariant Predictions for Planck-Scale Features in Primordial Power Spectra

TL;DR

This paper predicts small oscillatory corrections to primordial power spectra from covariant quantum gravity cutoffs, offering a new way to test quantum gravity effects through cosmological observations.

Contribution

It introduces a covariant method to incorporate ultraviolet cutoffs in primordial correlator calculations, providing explicit predictions without assuming specific inflationary potentials.

Findings

Oscillations depend on cutoff scale and slow-roll parameter

Predictions are testable via cosmic microwave background observations

Potential to set bounds on quantum gravity scale

Abstract

In this companion to our letter (arXiv:2208.10514), we elaborate the full details of the predicted corrections to the primordial scalar and tensor power spectra that arise from quantum gravity-motivated, natural, covariant ultraviolet cutoffs. We implement these cutoffs by covariantly restricting the fields which are summed over in the path integrals for the primordial correlators, and we discuss in detail the functional analytic techniques necessary for evaluating such path integrals. Our prediction, which is given in terms of measured cosmological parameters and without assuming any particular inflationary potential, is that the corrections take the form of small oscillations which are superimposed on the conventional power spectra. The frequency of these oscillations only depends on the location of the cutoff scale and the first inflationary slow-roll parameter, while the amplitude and phase are also moderately sensitive to how smoothly the cutoff turns on. The specificity of the new predictions offers an opportunity to significantly enhance experimental sensitivity in observations of the cosmic microwave background and large-scale structure. This may be used to place ever higher bounds on the scale at which quantum gravity effects become important in quantum field theory or may even provide positive evidence for quantum gravity effects.