Primordial power spectrum from Planck

Abstract

Using modified Richardson-Lucy algorithm we reconstruct the primordial power\nspectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature\nanisotropy data. In our analysis we use different combinations of angular power\nspectra from Planck to reconstruct the shape of the primordial power spectrum\nand locate possible features. Performing an extensive error analysis we found\nthe dip near $\\ell\\sim750-850$ represents the most prominent feature in the\ndata. Feature near $\\ell\\sim1800-2000$ is detectable with high confidence only\nin 217 GHz spectrum and is apparently consequence of a small systematic as\ndescribed in the revised Planck 2013 papers. Fixing the background cosmological\nparameters and the foreground nuisance parameters to their best fit baseline\nvalues, we report that the best fit power law primordial power spectrum is\nconsistent with the reconstructed form of the PPS at 2$\\sigma$ C.L. of the\nestimated errors (apart from the local features mentioned above). As a\nconsistency test, we found the reconstructed primordial power spectrum from\nPlanck temperature data can also substantially improve the fit to WMAP-9\nangular power spectrum data (with respect to power-law form of the PPS)\nallowing an overall amplitude shift of $\\sim2.5\\%$. In this context low-$\\ell$\nand 100 GHz spectrum from Planck which have proper overlap in the multipole\nrange with WMAP data found to be completely consistent with WMAP-9 (allowing\namplitude shift). As another important result of our analysis we do report the\nevidence of gravitational lensing through the reconstruction analysis. Finally\nwe present two smooth form of the PPS containing only the important features.\nThese smooth forms of PPS can provide significant improvements in fitting the\ndata (with respect to the power law PPS) and can be helpful to give hints for\ninflationary model building.\n