A Planck-scale axion and SU(2) Yang-Mills dynamics: Present acceleration and the fate of the photon

TL;DR

This paper explores a cosmological model where a Planck-scale axion coupled with an SU(2) Yang-Mills gauge theory explains current acceleration and predicts the future evolution of photon mass, suggesting a finite epoch of massless photons.

Contribution

It introduces a novel cosmological framework involving a strongly interacting SU(2) gauge theory and a Planck-scale axion to explain dark energy and photon mass evolution.

Findings

Predicts the current epoch of cosmological acceleration as driven by the axion-gauge system.

Estimates a 2.2 billion year upper limit for the duration of the massless photon epoch.

Discusses the compatibility of the model with cosmological and particle physics constraints.

Abstract

From the time of CMB decoupling onwards we investigate cosmological evolution subject to a strongly interacting SU(2) gauge theory of Yang-Mills scale $\Lambda\sim 10^{-4}$ eV (masquerading as the $U(1)_{Y}$ factor of the SM at present). The viability of this postulate is discussed in view of cosmological and (astro)particle physics bounds. The gauge theory is coupled to a spatially homogeneous and ultra-light (Planck-scale) axion field. As first pointed out by Frieman et al., such an axion is a viable candidate for quintessence, i.e. dynamical dark energy, being associated with today's cosmological acceleration. A prediction of an upper limit $\Delta t_{m_\gamma=0}$ for the duration of the epoch stretching from the present to the point where the photon starts to be Meissner massive is obtained: $\Delta t_{m_\gamma=0}\sim 2.2$ billion years.