New limits on the variability of G from big bang nucleosynthesis

Abstract

We revise limits on the value of G during primordial nucleosynthesis by incorporating new measurements of the neutron half-life along with the most recent reaction rate uncertainties. In doing this we follow D, 3He, and 7Li as G varies to determine how this variation affects limits on the baryon-to-photon ratio ( μ). We then incorporate these new limits into the 4He predictions to limit G as a function of the number of relativistic species at the time of nucleosynthesis. If the number of such species (⩾2) is not greater than the upper limit on the number of light neutrinos measured at CERN and the primordial abundance of 4He was between (22–25)%, then 1.4>G nucl G today >0.7 . If G( t) ≈ t − α , this would translate into a limit 0.008> α>−0.009, or an approximate limit ( G G ) today<±9×10 −13 yr −1 .