Eur. Phys. J. C (2007) 50: 635-646
https://doi.org/10.1140/epjc/s10052-007-0214-x

Regular Article - Theoretical Physics

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

Institut für Theoretische Physik, Universität Frankfurt, Johann Wolfgang Goethe-Universität, Max von Laue-Str. 1, 60438, Frankfurt, Germany

^* e-mail: R.Hofmann@thphys.uni-heidelberg.de

Received: 26 April 2006
Revised: 27 November 2006
Published online: 15 February 2007

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, Λ ∼ 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 ultralight (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 for Δt_mγ=0, the duration of the epoch stretching from the present to the point where the photon starts to be Meissner massive, is obtained: Δt_mγ=0∼2.2 billion years.