Linear inflation from quartic potential

TL;DR

This paper demonstrates that a non-minimally coupled inflaton with a dynamically generated Planck scale can produce inflationary predictions confined between quadratic and linear inflation, with linear inflation aligning with current observations.

Contribution

It introduces a scale-invariant inflationary model with a single free parameter that naturally leads to predictions between quadratic and linear inflation, highlighting the viability of linear inflation.

Findings

Predictions lie between quadratic and linear inflation.

Linear inflation matches current observational constraints.

The model's key parameter is the inflaton's non-minimal coupling to gravity.

Abstract

We show that if the inflaton has a non-minimal coupling to gravity and the Planck scale is dynamically generated, the results of Coleman-Weinberg inflation are confined in between two attractor solutions: quadratic inflation, which is ruled out by the recent measurements, and linear inflation which, instead, is in the experimental allowed region. The minimal scenario has only one free parameter -- the inflaton's non-minimal coupling to gravity -- that determines all physical parameters such as the tensor-to-scalar ratio and the reheating temperature of the Universe. Should the more precise future measurements of inflationary parameters point towards linear inflation, further interest in scale-invariant scenarios would be motivated.