Fine-structure constant constraints on dark energy

We use astrophysical and atomic clock tests of the stability of the fine-structure constant alpha, 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 zeta to the electromagnetic sector) the a variation. We show how current data tightly constrain a combination of zeta and the dark energy equation of state w(0). At the 95% confidence level and marginalizing over w(0) we find vertical bar zeta vertical bar < 5 x 10(-6), with the atomic clock tests dominating the constraints. The forthcoming generation of high-resolution ultrastable spectrographs will enable significantly tighter constraints.