Probing the primordial Universe from the low-multipole CMB data
  Since the temperature fluctuations in cosmic microwave background (CMB) on
large-angular scales probe length scales that were super-horizon sized at
photon decoupling and hence insensitive to microphysical processes, the
low-multipole CMB data are supposed to be a good probe to the physics of the
primordial Universe. In this letter we will constrain the cosmological
parameters in the base $\Lambda$CDM model with tensor perturbations by only
using low-multipole CMB data, including Background Imaging of Cosmic
Extragalactic Polarization (B2), Planck released in 2013 (P13) and Wilkinson
Microwaves Anisotropy Probe 9-year data (W9). We find that a red tilted power
spectrum of relic gravitational waves is compatible with the data, but a blue
tilted power spectrum of scalar perturbations on the large scales is preferred
at around $2\sigma$ confidence level.
