Natural cliff inflation

TL;DR

This paper introduces a new inflation model where the inflaton is an angular mode in a compactified extra dimension, featuring flat potentials that allow for sub-Planckian field excursions and align with observational data.

Contribution

It presents a novel inflation scenario with a lightest angular mode in extra dimensions, achieving flat potentials and observational consistency without hilltop initial conditions.

Findings

Predicts spectral index consistent with observations

Achieves tensor-to-scalar ratio within observational bounds

Realizes sub-Planckian field excursions naturally

Abstract

We propose a novel scenario of inflation, in which the inflaton is identified as the lightest mode of an angular field in a compactified fifth dimension. The periodic effective potential exhibits exponentially flat plateaus, so that a sub-Planckian field excursion without hilltop initial conditions is naturally realized. We can obtain consistent predictions with observations on the spectral index and the tensor-to-scalar ratio.