Large tensor-to-scalar ratio from Composite Inflation

TL;DR

This paper demonstrates that single-field composite inflation models can produce a large tensor-to-scalar ratio compatible with BICEP2 observations, given appropriate parameters and sufficient e-foldings.

Contribution

It shows that composite inflation models can naturally generate a large tensor-to-scalar ratio, expanding the viable inflationary scenarios consistent with recent data.

Findings

Large tensor-to-scalar ratio (r ≈ 0.20) achievable in composite inflation

Proper parameter choices yield sufficient e-foldings and compatibility with BICEP2

Composite models can match observational constraints on inflation

Abstract

The claimed detection of the BICEP2 experiment on the primordial B-mode of cosmic microwave background polarization suggests that cosmic inflation possibly takes place at the energy around the grand unified theory scale given a constraint on the tensor-to-scalar ratio. i.e., $r\simeq 0.20$. In this report, we revisit single-field (slow-roll) composite inflation and show that, with the proper choice of parameters and sizeable number of e-foldings, a large tensor-to-scalar ratio consistent with the recent BICEP2 results can be significantly produced with regard to the composite paradigms.