Power Spectrum of Inflationary Attractors

TL;DR

This paper explores inflationary attractors, especially universal attractors with non-minimal coupling, showing they predict specific relations between power spectrum amplitude, e-folds, and observable features like power loss at large scales.

Contribution

It demonstrates that inflationary attractors predict a specific relation between power spectrum amplitude and e-folds, linking the inflationary plateau's properties with observable parameters.

Findings

At least 55 e-foldings are predicted for observed power normalization.

The model accounts for power loss at large angular scales.

Predicts a relation between the amplitude of the power spectrum and the number of e-folds.

Abstract

Inflationary attractors predict the spectral index and tensor-to-scalar ratio to take specific values that are consistent with Planck. An example is the universal attractor for models with a generalised non-minimal coupling, leading to Starobinsky inflation. In this paper we demonstrate that it also predicts a specific relation between the amplitude of the power spectrum and the number of e-folds. The length and height of the inflationary plateau are related via the non-minimal coupling: in a wide variety of examples, the observed power normalisation leads to at least 55 flat e-foldings. Prior to this phase, the inflationary predictions vary and can account for the observational indications of power loss at large angular scales.