Red, Straight, no bends: primordial power spectrum reconstruction from CMB and large-scale structure

TL;DR

This paper introduces a minimally parametric, model-independent method to reconstruct the primordial power spectrum from diverse cosmological data, confirming the inflationary paradigm and disfavoring deviations like small-scale power suppression.

Contribution

It develops a smoothing spline technique for primordial spectrum reconstruction and applies it to multiple datasets, providing robust evidence for a power law spectrum with a red tilt.

Findings

Supports a power law primordial spectrum with a red tilt

Disfavors deviations such as small-scale power suppression

Confirms the inflationary paradigm

Abstract

We present a minimally parametric, model independent reconstruction of the shape of the primordial power spectrum. Our smoothing spline technique is well-suited to search for smooth features such as deviations from scale invariance, and deviations from a power law such as running of the spectral index or small-scale power suppression. We use a comprehensive set of the state-of the art cosmological data: {\it Planck} observations of the temperature and polarisation anisotropies of the cosmic microwave background, WiggleZ and Sloan Digital Sky Survey Data Release 7 galaxy power spectra and the Canada-France-Hawaii Lensing Survey correlation function. This reconstruction strongly supports the evidence for a power law primordial power spectrum with a red tilt and disfavours deviations from a power law power spectrum including small-scale power suppression such as that induced by significantly massive neutrinos. This offers a powerful confirmation of the inflationary paradigm, justifying the adoption of the inflationary prior in cosmological analyses.