Inflation from Broken Scale Invariance

TL;DR

This paper proposes an inflation model based on spontaneously broken global scale invariance, which naturally protects the inflaton potential and allows large field displacements, resulting in a scale-invariant perturbation spectrum consistent with CMB data.

Contribution

It introduces a novel inflationary framework leveraging broken scale invariance to stabilize the inflaton potential and produce observable predictions.

Findings

The model maintains slow-roll conditions over large field ranges.

It naturally produces a scale-invariant spectrum of perturbations.

The approach stabilizes the Planck scale through weak breaking of scale invariance.

Abstract

We construct a model of inflation based on a low-energy effective theory of spontaneously broken global scale invariance. This provides a shift symmetry that protects the inflaton potential from quantum corrections. Since the underlying scale invariance is non-compact, arbitrarily large inflaton field displacements are readily allowed in the low-energy effective theory. A weak breaking of scale invariance by almost marginal operators provides a non-trivial inflaton minimum, which sets and stabilizes the final low-energy value of the Planck scale. The underlying scale invariance ensures that the slow-roll approximation remains valid over large inflaton displacements, and yields a scale invariant spectrum of perturbations as required by the CMB observations.