WMAP 5-year constraints on time variation of $\alpha$ and $m_e$ in a   detailed recombination scenario
  We study the role of fundamental constants in an updated recombination scenario. We focus on the time variation of the fine structure constant, and the electron mass in the early Universe, and put bounds on these quantities by using data from CMB including WMAP 5-yr release and the 2dFGRS power spectrum. We analyze how the constraints are modified when changing the recombination scenario. 
Claudia G. Sc\'occola, Susana. J. Landau, and Hector Vucetich