OKLO vs. QSO: On time-variability of the fine structure constant

Akira Iwamoto, Japan Atomic Energy Research Institute

OKLO is a uranium mine located in the Republic of Gabon, midwest Africa, where a natural U(235)-based chain reaction occurred two billion years ago. A QSO (Quasi-Stellar Object) is a source of electro-magnetic radiation, the most distant one of which is located at a distance of more than 0.9 times the horizon of the Universe. There is currently an intense discussion on whether studies of these two objects can shed light on whether or not the fine structure constant varies with time.

Soon after the discovery of OKLO in 1972, A. Shlyakhter published a one-page contribution in Nature where he claimed from the nuclear-data analysis of the abundance of Sm(149) that the strengths of fundamental interactions 2Gy ago are the same as at present with an accuracy which is more stringent than what is obtained from any other measurements, for example the Os-Re decay rate, nuclear synthesis, comparison of atomic clocks, and so on. Since this upper bound sets the most stringent limit even today, we performed an extensive examination of his method using new, more reliable data from OKLO. We found two solutions, of which the "null solution" puts Shlyakhter's results on firmer ground. The other, "non-null solution," appears to be excluded from additional studies of Gadolinium data.

In contrast, during the last two years, a group of scientists are claiming that they find a definite difference between the fine-structure constant of the QSO era and its present value, based on QSO spectroscopy. Since the difference they deduce is two orders of magnitude larger than the upper bound found from OKLO data, these issues are currently intensely debated. I will briefly review these most recent developments.

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