Helical Inflation and Cosmic Strings

TL;DR

This paper proposes a helical axion inflation model consistent with recent BICEP2 results, highlighting its distinctive tensor-to-scalar ratio and exploring the potential contribution of cosmic strings to observed B-mode polarization.

Contribution

The paper introduces a helical axion inflation model that reduces to chaotic inflation and discusses its unique signatures and the possible role of cosmic strings in polarization signals.

Findings

The model predicts a smaller tensor/scalar ratio r, characteristic of axion periodicity.

A simple method to quantify the periodic signature in inflationary models.

Cosmic strings may contribute to B-mode polarization anisotropy.

Abstract

Recent BICEP2 detection of low-multipole B-mode polarization anisotropy in the cosmic microwave background radiation supports the inflationary universe scenario and suggests a large inflaton field range. The latter feature can be achieved with axion fields in the framework of string theory. We present such a helical model which naturally becomes a model with a single cosine potential, and which in turn reduces to the (quadratic) chaotic inflation model in the super-Planckian limit. The slightly smaller tensor/scalar ratio $r$ of models of this type provides a signature of the periodic nature of an axion potential. We present a simple way to quantify this distinctive feature. As axions are intimately related to strings/vortices and strings are ubiquitous in string theory, we explore the possibility that cosmic strings may be contributing to the B-mode polarization anisotropy observed.