Model-independent cosmological constraints from the CMB

TL;DR

This paper develops a model-independent analysis of CMB data, focusing on the last scattering surface and excluding low multipoles, to derive cosmological parameters with minimal assumptions.

Contribution

It introduces a method to analyze CMB data that minimizes model dependence by encoding late-time effects into a single parameter.

Findings

Derived cosmological parameters with specified uncertainties.

Observed systematic shifts when excluding low multipole data.

Found the angular scale of the sound horizon to be very well constrained.

Abstract

We analyse CMB data in a manner which is as model-independent as possible. We encode the effects of late-time cosmology into a single parameter which determines the distance to the last scattering surface. We exclude low multipoles $\ell<40$ from the analysis. We consider the WMAP5 and ACBAR data. We obtain the cosmological parameters $100\omega_b =2.13\pm 0.05$, $\omega_c=0.124\pm 0.007$, $n_s=0.93\pm 0.02$ and $\theta_A=0.593\pm 0.001$ degrees (68% C.L.). The last number is the angular scale subtended by the sound horizon at decoupling. There is a systematic shift in the parameters as more low $\ell$ data is omitted, towards smaller values of $\omega_b$ and $n_s$ and larger values of $\omega_c$. The scale $\theta_A$ remains stable and very well determined.