Fractional chaotic inflation in the lights of PLANCK and BICEP2

TL;DR

This paper explores fractional-chaotic inflation models with potentials of the form V_0 phi^(a/b), demonstrating their consistency with recent BICEP2 and PLANCK data and analyzing their spectral index and tensor-to-scalar ratio.

Contribution

It introduces fractional-chaotic inflationary potentials within supergravity, showing their compatibility with observational data and examining their spectral index and running.

Findings

Fractional-chaotic potentials can fit observational data within 1 sigma.

Supergravity realization of these potentials is possible with generalized shift symmetry.

Models with a/b between 2 and 3 predict observable tensor-to-scalar ratios.

Abstract

In the lights of current BICEP2 observations accompanied with the PLANCK satellite results, it has been observed that the simple single field chaotic inflationary models provide a good agreement with their spectral index n_s and large tensor-to-scalar ratio r (0.15 <r <0.26). To explore the other simple models, we consider the fractional-chaotic inflationary potentials of the form V_0 phi^(a/b) where a and b are relatively prime. We show that such kind of inflaton potentials can be realized elegantly in the supergravity framework with generalized shift symmetry and a nature bound a/b < 4 for consistency. Especially, for the number of e-folding from 50 to 60 and some a/b from 2 to 3, our predictions are nicely within at least 1 $\sigma$ region in the r-n_s plane. We also present a systematic investigation of such chaotic inflationary models with fractional exponents to explore the possibilities for the enhancement in the magnitude of running of spectral index (\alpha_{n_s}) beyond the simplistic models.