Constraints on the extensions to the base ΛCDM model from BICEP2, Planck and WMAP

Abstract

Recently Background Imaging of Cosmic Extragalactic Polarization (B2) discovered the relic gravitational waves at 7.0σ confidence level. However, the other cosmic microwave background (CMB) data, for example Planck data released in 2013 (P13), prefer a much smaller amplitude of the primordial gravitational waves spectrum if a power-law spectrum of adiabatic scalar perturbations is assumed in the six-parameter ΛCDM cosmology. In this paper, we explore whether the wCDM model and the running spectral index can relax the tension between B2 and other CMB data. Specifically we found that a positive running of running of spectral index is preferred at 1.7σ level from the combination of B2, P13 and WMAP Polarization data.