Natural Inflation with Hidden Scale Invariance

TL;DR

This paper introduces a natural inflation model based on hidden scale invariance, where quantum corrections lift flat directions in the potential, leading to specific predictions for inflationary parameters consistent with observations.

Contribution

It presents a novel inflation model utilizing hidden scale invariance that naturally produces a flat potential without fine-tuning, with specific testable predictions for cosmological parameters.

Findings

Predicted spectral index n_s-1 ≈ -0.025 (N_*/60)^-1

Predicted tensor-to-scalar ratio r ≈ 0.067 (N_*/60)^-1

Model aligns reasonably with current cosmological measurements

Abstract

We propose a new class of natural inflation models based on a hidden scale invariance. In a very generic Wilsonian effective field theory with an arbitrary number of scalar fields, which exhibits scale invariance via the dilaton, the potential necessarily contains a flat direction in the classical limit. This flat direction is lifted by small quantum corrections and inflation is realised without need for an unnatural fine-tuning. In the conformal limit, the effective potential becomes linear in the inflaton field, yielding to specific predictions for the spectral index and the tensor-to-scalar ratio, being respectively: $n_s-1\approx -0.025\left(\frac{N_{\star}}{60}\right)^{-1}$ and $r\approx 0.0667\left(\frac{N_{\star}}{60}\right)^{-1}$, where $N_{\star}\approx 30-65$ is a number of efolds during observable inflation. This predictions are in reasonable agreement with cosmological measurements. Further improvement of the accuracy of these measurements may turn out to be critical in falsifying our scenario.