Light Sterile Neutrinos and a High-Quality Axion from a Holographic Peccei-Quinn Mechanism

TL;DR

This paper introduces a 5D holographic model that unifies explanations for fermion mass hierarchy, a high-quality axion, and sterile neutrinos, predicting observable axion-neutrino interactions.

Contribution

It develops a novel 5D axion-neutrino framework with a holographic dual, explaining fermion hierarchies and producing a high-quality axion alongside light sterile neutrinos.

Findings

The model generates a high-quality axion from IR scale dynamics.

Sterile neutrinos can be Dirac or Majorana with small masses.

Predicted axion-neutrino couplings are testable experimentally.

Abstract

We present a 5D axion-neutrino model that explains the Standard Model fermion mass hierarchy and flavor structure, while simultaneously generating a high-quality axion. The axion and right-handed neutrinos transform under a 5D Peccei-Quinn gauge symmetry, and have highly suppressed profiles on the UV brane where the symmetry is explicitly broken. This setup allows neutrinos to be either Dirac, or Majorana with hierarchically small sterile neutrino masses. The axion decay constant originates from the IR scale, which in the holographically dual 4D description corresponds to the confinement scale of some new strong dynamics with a high-quality global Peccei-Quinn symmetry that produces a composite axion and light, composite sterile neutrinos. The sterile neutrinos could be observed in astrophysical or laboratory experiments, and the model predicts specific axion--neutrino couplings.