Coleman–Weinberg inflation in light of Planck

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 2σ 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 1σ  , 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−LB−L symmetry breaking together with a natural electroweak symmetry breaking can arise dynamically in a generalized B−LB−L extension of the Standard Model where the full potential is assumed to vanish at a high scale.