Inhomogeneous Big-Bang Nucleosynthesis in Light of Recent Observations

We consider inhomogeneous big bang nucleosynthesis in light of the present observational situation. Di erent observations of He and D disagree with each other, and depending on which set of observations one uses, the estimated primordial He corresponds to a lower baryon density in standard big bang nucleosynthesis than what one gets from deuterium. Recent Kamiokande results rule out a favorite particle physics solution to this tension between He and D. Inhomogeneous nucleosynthesis can alleviate this tension, but the more likely solution is systematics in the observations. The upper limit to b from inhomogeneous nucleosynthesis is higher than in standard nucleosynthesis, given that the distance scale of the inhomogeneity is near the optimal value, which maximizes effects of neutron di usion. Possible sources of baryon inhomogeneity include the QCD and electroweak phase transitions. The distance scale of the inhomogeneities arising from the electroweak transition is too small for them to have a large effect on nucleosynthesis, but the e ect may still be larger than some of the other small corrections recently incorporated to SBBN codes.