Possible constraints on the time variation of the fine structure constant from cosmic microwave background data

The formation of the cosmic microwave background radiation (CMBR) provides a very powerful probe of the early universe at the epoch of recombination. Specifically, it is possible to constrain the variation of fundamental physical constants in the early universe. We calculate the effect of a varying electromagnetic coupling constant (α) on the CMBR and find that new satellite experiments should provide a tight constraint on the value of α at recombination which is complementary to existing constraints. An estimate of the obtainable precision is | ̇ \.α/α|<~7×10^-13 yr^-1 in a realistic experiment.