Does Planck really rule out monomial inflation?

Abstract

We consider the modifications of monomial chaotic inflation models due to radiative corrections induced by inflaton couplings to bosons and/or fermions necessary for reheating. To the lowest order, ignoring gravitational corrections and treating the inflaton as a classical background field, they are of the Coleman-Weinberg type and parametrized by the renormalization scale $\mu$. In cosmology, there are not enough measurements to fix $\mu$ so that we end up with a family of models, each having a slightly different slope of the potential. We demonstrate by explicit calculation that within the family of chaotic $\phi^2$ models, some may be ruled out by Planck whereas some remain perfectly viable. In contrast, radiative corrections do not seem to help chaotic $\phi^{4}$ models to meet the Planck constraints.