Primordial Nucleosynthesis as a test of variable rest masses 5-dimensional cosmology
The deviation of primordial Helium production due to a variation on the difference between the rest masses of the nucleons is presented. It is found an upper bound $δ(M_{_n} - M_{_p}) \alt 0.129$ MeV, between the present and nucleosynthesis epochs. This bound is used to analyze Wesson's theory of gravitation; as a result, it is ruled out by observation.