Reexamination of the¹⁸⁷Re bound on the variation of fundamental couplings

We reconsider the ¹⁸⁷Re bound on the variation of the fine-structure constant. We combine the meteoritic measurement with several present-day lab measurements to firmly establish the quantitative upper limit to the time variation over the age of the solar system. We find that the relative change of the fine-structure constant between its present value and α of ∼4.6 Gyr ago is consistent with zero, Δα/α=[-8±8 (1σ)]×10^-7. We also rederive this bound in models where all gauge and Yukawa couplings vary in an interdependent manner, as would be expected in unified theories.