Constraining Antimatter Domains in the Early Universe with Big Bang Nucleosynthesis
Abstract
We consider the effect on big bang nucleosynthesis of a small-scale matter-antimatter domain structure (with more matter than antimatter) in the early universe. Depending on the size of the antimatter domains, antimatter annihilates before, during, or after nucleosynthesis. We place upper limits on the amount of antimatter at various domain sizes based on the abundances of light elements. For small domains, which annihilate before nucleosynthesis, the upper limit comes from underproduction of He-4. For larger domains, the limit comes from He-3 overproduction. Most of the He-3 from antiproton-helium annihilation is unable to escape far enough from the annihilation zone, and is annihilated later. The main source of He-3 is photodisintegration of He-4 by the electromagnetic cascades initiated by the high-energy photons and electrons produced by annihilation.Keywords
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