Reconstruction of the primordial power spectra with Planck and BICEP2

摘要: By using the cubic spline interpolation method, we reconstruct the shape of the primordial scalar and tensor power spectra from the recently released Planck temperature and BICEP2 polarization cosmic microwave background data. We find that the vanishing scalar index running (dns/d ln k) model is strongly disfavored at more than 3σ confidence level on the k = 0.0002 Mpc−1 scale. Furthermore, the power-law parameterization gives a blue-tilt tensor spectrum, no matter using only the first 5 bandpowers nt = 1.20+0.56 (95%CL) or the full 9 bandpowers nt = 1.24+0.51 (95%CL) of−0.64 −0.58BICEP2 data sets. Unlike the large tensor-to-scalar ratio value (r 0.20) under the scale-invariant tensor spectrum assumption, our interpolation approach gives r0.002 < 0.060 (95%CL) by using the first 5 bandpowers of BICEP2 data. After comparing the results with/without BICEP2 data, we find that Planck temperature with small tensor amplitude signals and BICEP2 polarization data with large tensor amplitude signals dominate the tensor spectrum reconstruction on the large and small scales, respectively. Hence, the resulting blue tensor tilt actually reflects the tension between Planck and BICEP2 data.