Maximum entropy deconvolution of primordial power spectrum

Abstract

It is well known that cosmic microwave background (CMB) temperature anisotropies and polarization can be used to probe the metric perturbations in the early universe. Presently, there exists no observational detection of tensor modes of primordial metric perturbations or of primordial non-Gaussianity. In such a scenario, the primordial power spectrum of scalar metric perturbations is the only correlation function of metric perturbations (presumably generated during inflation) whose effects can be directly probed through various observations. To explore the possibility of any deviations from the simplest picture of the era of cosmic inflation in the early universe, it thus becomes extremely important to uncover the amplitude and shape of this correlation sufficiently well. In the present work, we attempt to reconstruct the primordial power spectrum of scalar metric perturbations using the binned (uncorrelated) CMB temperature anisotropies data from WMAP 9-Year, using the maximum entropy method or MEM to solve the corresponding inverse problem. Our analysis shows that, given the current CMB data, there are no convincing reasons to believe that the primordial power spectrum of scalar metric perturbations has any significant features.