The Axion from Five-Dimensional Supergravity

TL;DR

This paper investigates the properties of the axion in five-dimensional supergravity models with boundaries, estimating the energy scale and discussing implications for the strong-CP problem and matter couplings.

Contribution

It provides an approximate effective action for the axion in 5D supergravity and analyzes how bulk geometry affects the Peccei-Quinn scale and related phenomenological bounds.

Findings

Flat bulk yields a lower bound on the axion scale.

Warped bulk can achieve the standard axion window.

Scalar potential may threaten the strong-CP solution.

Abstract

We consider the axion arising from five-dimensional supergravity in the presence of boundaries. We find the approximate bosonic effective action to estimate the lower bound on the "Peccei-Quinn" energy scale with a flat bulk. With a warped bulk, one can obtain a scale within the standard window; this puts a bound on the required curvature scale relative to the proper separation between boundaries. We comment on the scalar potential that may ruin the strong-CP resolution, and the effective derivative coupling to matter in 5D hypermultiplets.