New limits on Early Dark Energy from the South Pole Telescope
  We present new limits on early dark energy (EDE) from the cosmic microwave
background (CMB) using data from the WMAP satellite on large angular scales and
South Pole Telescope (SPT) on small angular scales. We find a strong upper
limit on the EDE density of Omega_e < 0.018 at 95% confidence, a factor of
three improvement over WMAP data alone. We show that adding lower-redshift
probes of the expansion rate to the CMB data improves constraints on the dark
energy equation of state, but not the EDE density. We also explain how the
small-scale CMB temperature anisotropy constrains EDE.
