Gravity Waves and Linear Inflation from Axion Monodromy

TL;DR

This paper explores how axion monodromy in string theory can naturally produce linear inflation potentials, compatible with moduli stabilization, and predicts observable gravitational wave signatures in the CMB.

Contribution

It demonstrates a broad class of string compactifications where axion monodromy yields linear inflation potentials consistent with stabilization and observable predictions.

Findings

Potential is linear in the canonical inflaton field.

Predicts tensor-to-scalar ratio r=0.07.

Compatible with various compactification geometries.

Abstract

Wrapped branes in string compactifications introduce a monodromy that extends the field range of individual closed-string axions to beyond the Planck scale. Furthermore, approximate shift symmetries of the system naturally control corrections to the axion potential. This suggests a general mechanism for chaotic inflation driven by monodromy-extended closed-string axions. We systematically analyze this possibility and show that the mechanism is compatible with moduli stabilization and can be realized in many types of compactifications, including warped Calabi-Yau manifolds and more general Ricci-curved spaces. In this broad class of models, the potential is linear in the canonical inflaton field, predicting a tensor to scalar ratio r=0.07 accessible to upcoming cosmic microwave background (CMB) observations.