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A new mechanism for enhancing the helium abundance in the blue main sequencestars of omega Centauri and NGC 2808 is investigated. We suggest that heliumenhancement was caused by the inhomogeneous big bang nucleosynthesis. Regionswith extremely high baryon-to-photon ratios are assumed to be caused by thebaryogenesis. Its mass scale is also assumed to be 10^6 Msun. An example of themechanisms to realize these two things was already proposed as the Affleck-Dinebaryogenesis. As the baryon-to-photon ratio becomes larger, the primordialhelium abundance is enhanced. We calculated the big bang nucleosynthesis andfound that there exists a parameter region yielding enough helium to accountfor the split of the main sequence in the aforementioned globular clusterswhile keeping the abundances of other elements compatible with observations.Our mechanism predicts that heavy elements with the mass number of around 100is enhanced in the blue main sequence stars. We estimate the timescales ofdiffusion of the enhanced helium and mass accretion in several stages after thenucleosynthesis to investigate whether these processes diminish the enhancementof helium. We found that the diffusion does not influence the helium content. Acloud with a sufficiently large baryon-to-photon ratio to account for themultiple main sequence collapsed immediately after the recombination.Subsequently, the cloud accreted the ambient matter with the normal heliumcontent. If the star formation occurred both in the collapsed core and theaccreted envelope, then the resultant star cluster has a double main sequence.

Multiple Main Sequence of Globular Clusters as a Result of Inhomogeneous Big Bang Nucleosynthesis