Axion Quality in Warped Extra-Dimension

TL;DR

This paper analyzes how warped extra-dimensional models influence the axion quality problem, focusing on nonlocal effects and geometric factors that suppress symmetry-breaking contributions to the axion potential.

Contribution

It systematically computes nonlocal contributions to the axion potential in warped geometries and classifies conditions for high axion quality.

Findings

Warped geometry and orbifold fixed points affect axion potential contributions.

Nonlocal effects mediated by charged fields are dominant sources of symmetry breaking.

Conditions for achieving sufficiently high axion quality are identified.

Abstract

We investigate the axion quality problem in warped extra-dimensional models in which the QCD axion arises as the Wilson-line mode of a five-dimensional $U(1)$ gauge field compactified on an $S^1/\mathbb{Z}_2$ orbifold. Higher-dimensional gauge invariance severely constrains possible sources of Peccei--Quinn symmetry breaking, implying that non-QCD contributions to the axion potential are predominantly generated by nonlocal effects mediated by $U(1)$-charged fields propagating along the compact dimension. We systematically compute these contributions and examine how both the warped geometry and the orbifold fixed points (branes) affect the resulting axion quality. Finally, we classify the parametric suppression of the induced axion potential, thereby identifying the conditions under which warped extra-dimensional axions can achieve sufficiently high quality.