2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/182930From the time of CMB decoupling onwards we investigate cosmological evolution subject to a strongly interacting SU(2) gauge theory of Yang-Mills scale $Λ\sim 10^{-4}$ 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 $Δt_{m_γ=0}$ for the duration of the epoch stretching from the present to the point where the photon starts to be Meissner massive is obtained: $Δt_{m_γ=0}\sim 2.2$ billion years.v3: consequences of an error in evolution equation for coupling rectified, only a minimal change in physics results, two refs. addedHigh Energy Physics - Theorytext