Constraining Antimatter Domains in the Early Universe with Big Bang Nucleosynthesis

We consider the effect of a small-scale matter-antimatter domain structure on big bang nucleosynthesis and place upper limits on the amount of antimatter in the early universe. For small domains, which annihilate before nucleosynthesis, this 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 annihilated also. The main source of He-3 is photodisintegration of He-4 by the electromagnetic cascades initiated by the annihilation.Comment: 4 pages, 2 figures, revtex, (slightly shortened

Antimatter Regions in the Early Universe and Big Bang Nucleosynthesis

We have studied big bang nucleosynthesis in the presence of regions of antimatter. Depending on the distance scale of the antimatter region, and thus the epoch of their annihilation, the amount of antimatter in the early universe is constrained by the observed abundances. Small regions, which annihilate after weak freezeout but before nucleosynthesis, lead to a reduction in the 4He yield, because of neutron annihilation. Large regions, which annihilate after nucleosynthesis, lead to an increased 3He yield. Deuterium production is also affected but not as much. The three most important production mechanisms of 3He are 1) photodisintegration of 4He by the annihilation radiation, 2) pbar-4He annihilation, and 3) nbar-4He annihilation by "secondary" antineutrons produced in anti-4He annihilation. Although pbar-4He annihilation produces more 3He than the secondary nbar-4He annihilation, the products of the latter survive later annihilation much better, since they are distributed further away from the annihilation zone.Comment: 15 pages, 9 figures. Minor changes to match the PRD versio

The spatio-ecological segregation of different cytotypes of <I>Oxalis obtusa</I> (Oxalidaceae) in contact zones

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Two new species of <I>Oxalis</I> (Oxalidaceae) from the Greater Cape Floristic Region

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Cytogeography of <I>Oxalis</I><I> pes-caprae </I>in its native range: where are the pentaploids?

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Extensive sampling and high-throughput sequencing reveal Posidoniomyces atricolor gen. et sp. nov. (Aigialaceae, Pleosporales) as the dominant root mycobiont of the dominant Mediterranean seagrass Posidonia oceanica

Volume: 55Start Page: 59End Page: 8

High ploidy diversity and distinct patterns of cytotype distribution in a widespread species of <I>Oxalis</I> in the Greater Cape Floristic Region

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The GRAAL experiment: Beam polarization asymmetries in pseudoscalar meson photoproduction

The GRAAL tagged and polarized gamma beam has been operating with a maximum energy of 1100 MeV. For the first time asymmetry results in eta photoproduction were obtained and will be shown. Interesting results have also been obtained for pi(0) and pi(+) photo-production, that largely confirm the already existing ones, but also extend in not yet explored angular and energetic regions, especially for backward scattering and energies greater than 900 MeV