Hierarchical Axion Inflation

TL;DR

This paper introduces a novel two-axion inflation model that achieves an effective trans-Planckian decay constant from sub-Planckian parameters, enabling inflation within a sub-Planckian field space with minimal tuning.

Contribution

It presents a new mechanism using two axions and hierarchical decay constants to realize inflation without super-Planckian field excursions, compatible with string theory embeddings.

Findings

Effective trans-Planckian decay constant generated from sub-Planckian parameters

Inflation occurs entirely within a sub-Planckian domain

Minimal tuning required for the model

Abstract

We propose a new field theory mechanism for generating an effective trans-Planckian decay constant from sub-Planckian ones. Using the minimal two axions and a hierarchy between two axion decay constants is sufficient for realizing inflation through non-perturbative effects only and with minimal tuning. The inflationary motion is kept entirely within a sub-Planckian domain. We outline possible strategies of embedding the model in a string theory setup.