Axion quality from the (anti)symmetric of SU(N)

TL;DR

This paper introduces two models where the Peccei-Quinn symmetry naturally emerges and remains intact against high-dimensional operators, ensuring the axion solves the strong CP problem even with Planck-scale effects, and explores associated dark matter candidates.

Contribution

It presents novel SU(N)-based models with accidental PQ symmetry, detailing conditions for axion quality and dark matter production mechanisms.

Findings

Axion quality requires N ≥ 10 in the first model.

Dark matter includes axions and monopoles or super-heavy relics.

Cosmological relic abundance can be achieved via inflation timing and decay processes.

Abstract

We propose two models where a U(1) Peccei-Quinn global symmetry arises accidentally and is respected up to high-dimensional operators, so that the axion solution to the strong CP problem is successful even in the presence of Planck-suppressed operators. One model is SU$(N)$ gauge interactions with fermions in the fundamental and a scalar in the symmetric. The axion arises from spontaneous symmetry breaking to SO$(N)$, that confines at a lower energy scale. Axion quality in the model needs $N \gtrsim 10$. SO bound states and possibly monopoles provide extra Dark Matter candidates beyond the axion. In the second model the scalar is in the anti-symmetric: SU$(N)$ broken to Sp$(N)$ needs even $N \gtrsim 20$. The cosmological DM abundance, consisting of axions and/or super-heavy relics, can be reproduced if the PQ symmetry is broken before inflation (Boltzmann-suppressed production of super-heavy relics) or after (super-heavy relics in thermal equilibrium get partially diluted by dark glue-ball decays).