Fine-structure constant constraints on dark energy

We use astrophysical and atomic clock tests of the stability of the fine-structure constant, together with type Ia supernova and Hubble parameter data, to constrain the simplest class of dynamical dark energy models where the same degree of freedom is assumed to provide both the dark energy and (through a dimensionless coupling to the electromagnetic sector) the variation. We show how current data tightly constrain a combination of and the dark energy equation of state w₀. At the 95% confidence level and marginalizing over w₀ we find ||<510^-6, with the atomic clock tests dominating the constraints. The forthcoming generation of high-resolution ultrastable spectrographs will enable significantly tighter constraints.