Reconstruction of the primordial power spectrum from CMB data

TL;DR

This study reconstructs the primordial power spectrum from CMB data, confirming a power-law shape and disfavoring the Harrison-Zel'dovich spectrum, supporting inflationary models without features.

Contribution

It introduces a binning method using cubic spline interpolation to reconstruct the primordial power spectrum from CMB data.

Findings

Power-law spectrum is preferred over Harrison-Zel'dovich at 95% confidence.

No evidence found for features in the primordial power spectrum.

Simpler models without tensor modes are favored by the data.

Abstract

Measuring the deviation from scale invariance of the primordial power spectrum is a critical test of inflation. In this paper we reconstruct the shape of the primordial power spectrum of curvature perturbations from the cosmic microwave background data, including the 7-year Wilkinson Microwave Anisotropy Probe data and the Atacama Cosmology Telescope 148 GHz data, by using a binning method of a cubic spline interpolation in log-log space. We find that the power-law spectrum is preferred by the data and that the Harrison-Zel'dovich spectrum is disfavored at 95% confidence level. These conclusions hold with and without allowing for tensor modes, however the simpler model without tensors is preferred by the data. We do not find evidence for a feature in the primordial power spectrum - in full agreement with generic predictions from cosmological inflation.