The Simple Single Field Inflation Models and the Running of Spectral Index

TL;DR

This paper investigates simple single-field inflation models to reconcile BICEP2's detection of primordial gravitational waves with Planck data, focusing on the spectral index running, but finds limitations in achieving the required running.

Contribution

It introduces two simple single-field inflation models, including one based on supergravity, to examine their compatibility with recent observational data.

Findings

Models fit tensor-to-scalar ratio and spectral index but cannot produce the large negative running needed.

Supergravity-based models fail to generate the required spectral index running.

The study highlights challenges in constructing inflation models consistent with all current observations.

Abstract

The BICEP2 experiment confirms the existence of primordial gravitational wave with the tensor-to-scalar ratio $r=0$ ruled out at $7\sigma$ level. The consistency of this large value of $r$ with the {\em Planck} data requires a large negative running $n'_s$ of the scalar spectral index. Herein we propose two types of the single field inflation models with simple potentials to study the possibility of the consistency of the models with the BICEP2 and {\em Planck} observations. One type of model suggested herein is realized in the supergravity model building. These models fail to provide the needed $n'_s$ even though both can fit the tensor-to-scalar ratio and spectral index.