NUCLEOSYNTHESIS AND THE TIME-DEPENDENCE OF FUNDAMENTAL COUPLINGS

We consider the effects of the time dependence of couplings due to the ir dependence on a dilaton field, as occurs in superstring theory, as well as in gravity theories of the Jordan-Brans-Dicke type. Because th e scale parameters of couplings set by dimensional transmutation depen d exponentially on the dilaton vev, we may obtain stringent limits on the shift of the dilaton from the requirement that the induced shift i n the couplings not vitiate the successful calculations of element abu ndances for big-bang nucleosynthesis. These limits can be substantiall y stronger than those obtained directly from the dilaton-induced chang e in the gravitational coupling.