Features from the non-attractor beginning of inflation

TL;DR

This paper investigates how a non-attractor initial phase in single-field inflation influences the primordial power spectrum and non-Gaussianity, producing features that align with recent observational data.

Contribution

It provides a detailed analysis of the effects of a brief non-attractor phase on inflationary predictions, including power spectrum suppression and non-Gaussianity features.

Findings

Large scale suppression in the primordial power spectrum.

Step features in local and equilateral non-Gaussianity shapes.

Initial non-attractor phase can produce observable inflationary features.

Abstract

We study the effects of the non-attractor initial conditions for the canonical single-field inflation. The non-attractor stage can last only several $e$-folding numbers, and should be followed by hilltop inflation. This two-stage evolution leads to large scale suppression in the primordial power spectrum, which is favored by recent observations. Moreover we give a detailed calculation of primordial non-Guassianity due to the "from non-attractor to slow-roll" transition, and find step features in the local and equilateral shapes. We conclude that a plateau-like inflaton potential with an initial non-attractor phase yields interesting features in both power spectrum and bispectrum.