(Lack of) Cosmological evidence for dark radiation after Planck
  We use Bayesian model comparison to determine whether extensions to
Standard-Model neutrino physics -- primarily additional effective numbers of
neutrinos and/or massive neutrinos -- are merited by the latest cosmological
data. Given the significant advances in cosmic microwave background (CMB)
observations represented by the Planck data, we examine whether Planck
temperature and CMB lensing data, in combination with lower redshift data, have
strengthened (or weakened) the previous findings. We conclude that the
state-of-the-art cosmological data do not show evidence for deviations from the
standard cosmological model (which has three massless neutrino families). This
does not mean that the model is necessarily correct -- in fact we know it is
incomplete as neutrinos are not massless -- but it does imply that deviations
from the standard model (e.g., non-zero neutrino mass) are too small compared
to the current experimental uncertainties to be inferred from cosmological data
alone.
