Natural Inflation from 5D SUGRA and Low Reheat Temperature

TL;DR

This paper revisits a 5D supergravity-based natural inflation model motivated by recent cosmological data, highlighting its low reheating temperature, slow inflaton decay, and compatibility with Planck 2015 results.

Contribution

It provides a detailed analysis of a supersymmetric 5D natural inflation model with a low reheating temperature, connecting high-energy theory with cosmological observations.

Findings

Reheating temperature is estimated to be below 100 GeV.

The model predicts spectral index values consistent with Planck 2015 data.

The inflaton decay rate is very slow due to gauge coupling constraints.

Abstract

Motivated by recent cosmological observations of a possibly unsuppressed primordial tensor component $r$ of inflationary perturbations, we reanalyse in detail the 5D conformal SUGRA originated natural inflation model of Ref. [1]. The model is a supersymmetric variant of 5D extra natural inflation, also based on a shift symmetry, and leads to the potential of natural inflation. Coupling the bulk fields generating the inflaton potential via a gauge coupling to the inflaton with brane SM states we necessarily obtain a very slow gauge inflaton decay rate and a very low reheating temperature $T_r\stackrel{<}{_\sim }{\cal O}(100)$~GeV. Analysis of the required number of e-foldings (from the CMB observations) leads to values of $n_s$ in the lower range of present Planck 2015 results. Some related theoretical issues of the construction, along with phenomenological and cosmological implications, are also discussed.