Accidental SO(10) axion from gauged flavour

TL;DR

This paper proposes a natural SO(10) grand unified theory where an accidental Peccei-Quinn symmetry arises, providing a high-quality axion solution to the strong CP problem with specific mass predictions and addressing the PQ quality issue.

Contribution

It introduces a novel SO(10) model with gauged flavor symmetry that naturally generates a high-quality axion, reducing the PQ quality problem and predicting axion mass ranges.

Findings

Axion mass window predicted as [7×10^{-8}, 10^{-3}] eV.

High-quality axion achievable for masses above 0.02 eV.

PQ quality problem addressed within a grand unified framework.

Abstract

An accidental U(1) Peccei-Quinn (PQ) symmetry automatically arises in a class of SO(10) unified theories upon gauging the SU(3)$_{f}$ flavour group. The PQ symmetry is protected by the $\mathbb{Z}_4 \times \mathbb{Z}_3$ center of $\text{SO(10)} \times \text{SU(3)}_f$ up to effective operators of canonical dimension six. However, high-scale contributions to the axion potential posing a PQ quality problem arise only at $d=9$. In the pre-inflationary PQ breaking scenario the axion mass window is predicted to be $m_a \in [7 \times 10^{-8}, 10^{-3}]$ eV, where the lower end is bounded by the seesaw scale and the upper end by iso-curvature fluctuations. A high-quality axion, that is immune to the PQ quality problem, is obtained for $m_a \gtrsim 0.02$ eV. We finally offer a general perspective on the PQ quality problem in grand unified theories.