New Constraints on variations of the fine structure constant from CMB anisotropies

TL;DR

This paper uses recent CMB measurements from multiple experiments to tighten constraints on potential variations of the fine structure constant in the early universe, achieving sub-percent accuracy.

Contribution

It provides the most precise constraints to date on the variation of the fine structure constant using combined CMB and HST data.

Findings

Constraints on alpha/alpha_0 are now within 1% of the current value.

Inclusion of HST data improves the constraint accuracy by a factor of three.

Possible deviations from the current fine structure constant are below 1%.

Abstract

We demonstrate that recent measurements of Cosmic Microwave Background temperature and polarization anisotropy made by the ACBAR, QUAD and BICEP experiments substantially improve the cosmological constraints on possible variations of the fine structure constant in the early universe. This data, combined with the five year observations from the WMAP mission yield the constraint alpha/alpha_0 = 0.987 \pm 0.012 at 68% c.l.. The inclusion of the new HST constraints on the Hubble constant further increases the accuracy to alpha/alpha_0 = 1.001 \pm 0.007 at 68% c.l., bringing possible deviations from the current value below the 1% level and improving previous constraints by a factor 3.