NAOJ-Th/ astro-ph/—– Geometrical Effects of Baryon Density Inhomogeneities on Primordial Nucleosynthesis

We discuss effects of fluctuation geometry on primordial nucleosynthesis. For the first time we consider condensed cylinder and cylindrical-shell fluctuation geometries in addition to condensed spheres and spherical shells. We find that a cylindrical shell geometry allows for an appreciably higher baryonic contribution to be the closure density (Ωbh50 < ∼ 0.2) than that allowed in spherical inhomogeneous or standard homogeneous big bang models. This result, which is contrary to some other recent studies, is due to both geometry and recently revised estimates of the uncertainties in the observationally inferred primordial light-element abundances. We also find that inhomogeneous primordial nucleosynthesis in the cylindrical shell geometry can lead to significant Be and B production. In particular, a primordial beryllium abundance as high as [Be] = 12 + log(Be/H) ≈ −3 is possible while still satisfying all of the light-element abundance constraints. Subject headings: cosmology: theory dark matter early universe nuclear reactions, nucleosynthesis, abundances Department of Astronomical Science, The Graduate University for Advanced Studies, Mitaka, Tokyo 181, Japan Division of Theoretical Astrophysics, National Astronomical Observatory, Mitaka, Tokyo 181, Japan Department of Physics, Department of Astronomy, Ohio State University, Columbus, OH 43210 Department of Physics, University of Notre Dame, Notre Dame, IN 46556 Institute for Nuclear Theory, University of Washington, Seattle, WA 98195