“…If the dark energy is described by a quintessence field, φ, non-minimally coupled to the electromagnetic field [29,30,31,32,33,34,35,36,37,38,39,40,41] then the dynamics of α is coupled to the evolution of φ. It was shown [42] that, under certain assumptions, varying couplings may be used to probe the nature of dark energy over a larger redshift range than that spanned by standard methods (such as supernovae [1,2,3,4] or weak lensing [43,44,45]).…”