Inflation and classical scale invariance

TL;DR

This paper proposes a scale-invariant inflationary model that naturally explains the absence of large operators and predicts a range of tensor-to-scalar ratios, testable by future CMB observations.

Contribution

It introduces a simple, gauge-group-free inflation model based on classical scale invariance, linking trans-Planckian inflaton values to observable tensor modes.

Findings

Model predicts a wide range of tensor-to-scalar ratios.

Classical scale invariance addresses the absence of large operators.

Future measurements of $r$ can test the model's validity.

Abstract

BICEP2 measurement of primordial tensor modes in CMB suggests that cosmological inflation is due to a slowly rolling inflaton taking trans-Planckian values and provides further experimental evidence for the absence of large $M_{\rm P}$ induced operators. We show that classical scale invariance solves the problem and allows for a remarkably simple scale-free inflaton model without any gauge group. Due to trans-Planckian inflaton values and VEVs, a dynamically induced Coleman-Weinberg-type inflaton potential of the model can predict tensor-to-scalar ratio $r$ in a large range. Precise determination of $r$ in future experiments will allow to test the proposed field-theoretic framework.