Distinguishing between Extra Natural Inflation and Natural Inflation after BICEP2

TL;DR

This paper compares natural and extra natural inflation models by calculating key spectral parameters and assesses the potential for future observations to distinguish between these inflation scenarios.

Contribution

The study provides detailed predictions of spectral indices for both models and evaluates the observational prospects for differentiating them.

Findings

Natural inflation predicts different spectral running than extra natural inflation.

Future measurements of the running spectral index could distinguish the models.

Distinguishing models using the running of running spectrum is more challenging but possible.

Abstract

In this paper, we carefully calculated the tensor-to-scalar ratio, the running spectral index, and the running of running spectrum for (extra) natural inflation in order to compare with recent BICEP2 data, PLANCK satellite data and future 21 cm data. We discovered that the prediction for running spectral index and the running of running spectrum in natural inflation is different from that in the case of extra natural inflation. Near future observation for the running spectral index may achieve enough accuracy to allow us distinguishing between extra natural inflation from natural inflation. Distinguishing the models by using the running of running spectrum is not impossible but would be more challenging for future experiments.