On Axionic Field Ranges, Loopholes and the Weak Gravity Conjecture

TL;DR

This paper clarifies how the Weak Gravity Conjecture constrains axion models of natural inflation, addressing recent concerns and emphasizing the difficulty of achieving inflation with axions under quantum gravity constraints.

Contribution

It provides a refined analysis of the impact of the Weak Gravity Conjecture on axion inflation models, clarifying previous results and addressing recent criticisms.

Findings

Weak Gravity Conjecture imposes significant constraints on axion inflation models

Recent attempts to evade these constraints face substantial difficulties

Axions remain challenging candidates for natural inflation under quantum gravity considerations

Abstract

In this short note we clarify some aspects of the impact that the Weak Gravity Conjecture has on models of (generalized) natural inflation. We address in particular certain technical and conceptual concerns recently raised regarding the stringent constraints and conclusions found in our previous work (arXiv:1503.04783). We also point out the difficulties faced by attempts to evade these constraints. These new considerations improve the understanding of the quantum gravity constraints we found and further support the conclusion that it remains challenging for axions to drive natural inflation.