Dark Energy, with Signatures
  We propose a class of simple dark energy models which predict a late-time
dark radiation component and a distinctive time-dependent equation of state
$w(z)$ for redshift $z < 3$. The dark energy field can be coupled strongly
enough to Standard Model particles to be detected in colliders, and the model
requires only modest additional particle content and little or no fine-tuning
other than a new energy scale of order milli-electron volts.
