Changing coupling ‘‘constants’’ and violation of the equivalence principle

Abstract
It is shown that a cosmological evolution of coupling ‘‘constants’’ due to a change in some dilaton field (such as the size of the extra dimensions in Kaluza-Klein theories or superstring theories), if observably large, would imply a long-range force of gravitational strength that would violate the equivalence principle. Our analysis is in the context of superstring theories but should be more general. We also clarify various obscurities and correct mistakes in the recent literature.