Coleman-Weinberg Inflation in light of Planck

TL;DR

This paper examines Coleman-Weinberg inflation models, highlighting the need for extremely small couplings, and explores how non-standard cosmologies like brane-world scenarios can align predictions with Planck data, also connecting to B-L symmetry breaking.

Contribution

It demonstrates that non-standard cosmological frameworks can reconcile Coleman-Weinberg inflation with observational data and links the model to B-L symmetry breaking within a Standard Model extension.

Findings

Small field Coleman-Weinberg inflation requires tiny quartic couplings.

Standard cosmology predicts a spectral index outside Planck's 2 sigma range.

Brane-world cosmology can bring the spectral index within 1 sigma of Planck data.

Abstract

We revisit a single field inflationary model based on Coleman-Weinberg potentials. We show that in small field Coleman-Weinberg inflation, the observed amplitude of perturbations needs an extremely small quartic coupling of the inflaton, which might be a signature of radiative origin. However, the spectral index obtained in a standard cosmological scenario turns out to be outside the 2 sigma region of the Planck data. When a non-standard cosmological framework is invoked, such as brane-world cosmology in the Randall-Sundrum model, the spectral index can be made consistent with Planck data within 1 sigma, courtesy of the modification in the evolution of the Hubble parameter in such a scheme. We also show that the required inflaton quartic coupling as well as a phenomenologically viable B-L symmetry breaking together with a natural electroweak symmetry breaking can arise dynamically in a generalized B-L extension of the Standard Model where the full potential is assumed to vanish at a high scale.