New nucleosynthesis constraint on the variation of G

The limits on possible variations in Newton's constant, G, were predicted using big bang nucleosynthesis (BBN) through constraints on the expansion rate. From the cosmic microwave background, an independent measurement of the baryon-to-photon ratio was obtained. A new tighter constraint on G was derived by combining this measurement with the measurements of primordial deuterium abundance in quasar absorption systems without recourse to considerations of helium or lithium abundances. The latter constraint was found to be stronger than the earlier measured BBN.