Search for features in the spectrum of primordial perturbations using Planck and other datasets

Abstract

We reconstruct the power spectrum of primordial curvature perturbations by applying a well-validated non-parametric technique employing Tikhonov regularisation to the first data release from the Planck satellite. To improve the reconstruction on small spatial scales we include data from the ground-based ACT and SPT experiments, the WiggleZ galaxy redshift survey, the CFHTLenS tomographic weak lensing survey, and spectral analysis of the Lyman-α forest. The reconstructed scalar spectrum (assuming the standard ΛCDM cosmology) is not scale-free but has an infrared cutoff at k ≲ 5 × 10^-4 Mpc^-1 and several (2-3)σ features, of which two at wavenumber k/Mpc^-1 0.0018 and 0.057 had been seen already in WMAP data. A higher significance feature at k ~ 0.12 Mpc^-1 is indicated by Planck data, but may be sensitive to the systematic uncertainty around multipole ℓ ~ 1800 in the 217×217 GHz cross-spectrum. In any case accounting for the 'look elsewhere' effect decreases its global significance to ~2σ.