Dark Radiation and Inflationary Freedom
  A relaxed primordial power spectrum (PPS) of scalar perturbations arising
from inflation can impact the dark radiation constraints obtained from Cosmic
Microwave Background and other cosmological measurements. If inflation produces
a non-standard PPS for the initial fluctuations, a fully thermalized light
sterile neutrino can be favoured by CMB observations, instead of being strongly
disfavoured. In the case of a thermal axion, the constraints on the axion mass
are relaxed when the PPS is different from the standard power law.
