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

Abstract

The constraints on the time variation of the fine structure constant at recombination epoch relative to its present value, $Δα/α\equiv (α_{\mathrm{rec}} - α_{\mathrm{now}})/α_{\mathrm{now}}$, 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 $Δα/α=-0.0009$ 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 $Δα/α$ are $-0.028 < Δα/α< 0.026$ with HST prior and $-0.050 < Δα/α< 0.042$ without HST prior.