Constraints on the time variation of the fine structure constant by the 5-year WMAP data

TL;DR

This study uses 5-year WMAP data to constrain how the fine structure constant may have varied over time, finding no significant deviation from its current value at the recombination epoch.

Contribution

It provides updated constraints on the time variation of the fine structure constant using the latest WMAP data and Markov-Chain Monte-Carlo analysis, with or without HST prior.

Findings

95% confidence range: -0.028 to 0.026 with HST prior

95% confidence range: -0.050 to 0.042 without HST prior

Mean variation: -0.0009, not significantly different from zero

Abstract

The constraints on the time variation of the fine structure constant at recombination epoch relative to its present value, $\Delta\alpha/\alpha \equiv (\alpha_{\mathrm{rec}} - \alpha_{\mathrm{now}})/\alpha_{\mathrm{now}}$, are obtained from the analysis of the 5-year WMAP cosmic microwave background data. As a result of Markov-Chain Monte-Carlo analysis, it is found that, contrary to the analysis based on the previous WMAP data, the mean value of $\Delta\alpha/\alpha=-0.0009$ does not change significantly whether we use the Hubble Space Telescope (HST) measurement of the Hubble parameter as a prior or not. The resultant 95% confidence ranges of $\Delta\alpha/\alpha$ are $-0.028 < \Delta\alpha/\alpha < 0.026$ with HST prior and $-0.050 < \Delta\alpha/\alpha < 0.042$ without HST prior.