Mapping the Dark Energy with Varying Alpha

Cosmological dark energy is a natural source of variation of the fine structure constant. Using a model-independent approach we show that once general assumptions about the alpha-varying interactions are made, astronomical probes of its variation constrain the dark energy equation of state today to satisfy -1 < w_f < -0.96 at 3-sigma and significantly disfavour late-time changes in the equation of state. We show how dark-energy-induced spatial perturbations of alpha are linked to violations of the Equivalence Principle and are thus negligible at low-redshift, in stark contrast to the BSBM theories. This provides a new test of dark energy as the source of alpha variation.