Nucleosynthesis Bounds on Jordan-Brans-Dicke Theories of Gravity

We reexamine the nucleosynthesis predictions for the simplest class of scalar-tensor theories of gravity, the Jordan-Brans-Dicke theory. Comparison with present observational data on light elements’ abundances provides bounds on the ω-parameter which are as strong as the post-Newtonian ones, or even stronger, depending on the value of Ωh2. Future improvements in the determination of the 4 He and D + 3 He abundances will increase this bound dramatically. We argue that a future (hypothetical) experimental deviation from general relativity prediction could be restored by a Jordan-Brans-Dicke theory.