Dark radiation as a signature of dark energy
  We propose a simple dark energy model with the following properties: the
model predicts a late-time dark radiation component that is not ruled out by
current observational data, but which produces a distinctive time-dependent
equation of state w(z) for 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.
