The fine-structure constant: a new observational limit on its cosmological variation and some theoretical consequences

Endeavours of the unification of the four fundamental interactions have resulted in a development of theories having cosmological solutions in which low-energy limits of fundamental physical constants vary with time. The validity of such theoretical models should be checked by comparison of the theoretical predictions with observational and experimental bounds on possible time-dependences of the fundamental constants. Based on high-resolution measurements of quasar spectra, we obtain the following direct limits on the average rate of the cosmological time variation of the fine-structure constant \alpha: |\dot{\alpha}/\alpha| < 1.9 \times 10^{-14} yr^{-1} is the most likely limit, and |\dot{\alpha}/\alpha| < 3.1 \times 10^{-14} yr^{-1} is the most conservative limit. Analogous estimates published previously, as well as other contemporary tests for possible variations of \alpha (those based on the "Oklo phenomenon", on the primordial nucleosynthesis models, and others) are discussed and compared with the present upper limit. We argue that the present result is the most conservative one.