Cosmological Parameters from Pre-Planck CMB Measurements

TL;DR

This paper analyzes pre-Planck CMB data from WMAP, ACT, and SPT, confirming the standard cosmological model and providing precise constraints on parameters like the spectral index and relativistic species.

Contribution

It combines multiple pre-Planck CMB datasets to refine measurements of cosmological parameters within the LCDM model.

Findings

Scalar spectral index n_s = 0.9690 +/- 0.0089

Effective number of relativistic species N_eff = 3.28 +/- 0.40

Data consistent with three light neutrino species

Abstract

Recent data from the WMAP, ACT and SPT experiments provide precise measurements of the cosmic microwave background temperature power spectrum over a wide range of angular scales. The combination of these observations is well fit by the standard, spatially flat LCDM cosmological model, constraining six free parameters to within a few percent. The scalar spectral index, n_s = 0.9690 +/- 0.0089, is less than unity at the 3.6 sigma level, consistent with simple models of inflation. The damping tail of the power spectrum at high resolution, combined with the amplitude of gravitational lensing measured by ACT and SPT, constrains the effective number of relativistic species to be N_eff = 3.28 +/- 0.40, in agreement with the standard model's three species of light neutrinos.