Since the temperature fluctuations in the 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 Λ CDM model with tensor perturbations by only using the low-multipole CMB data, including Background Imaging of Cosmic Extragalactic Polarization (B2), Planck data released in 2013 (P13) and Wilkinson Microwaves Anisotropy Probe 9-year data (W9). We find that either sign of the index of the tensor power spectrum is compatible with the data, but a blue-tilted power spectrum of scalar perturbations on large scales is preferred at around 2 σ confidence level.
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