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Nucleosynthesis in the presence of primordial isocurvature baryon fluctuations

  • Author(s): Jedamzik, K
  • Fuller, GM
  • et al.

Published Web Location

https://doi.org/10.1086/176278
Abstract

We study big bang nucleosynthesis in the presence of large mass scale, nonlinear entropy fluctuations. Overdense regions, with masses above the local baryon Jeans mass, are expected to collapse and form condensed objects. Surviving nucleosynthesis products therefore tend to originate from underdense regions. We compute expected survival light-element (2H, He, He, and Li) abundance yields for a variety of stochastic fluctuation spectra. In general, we find that spectra with significant power in fluctuations on mass scales below that of the local baryon Jeans mass (∼ 10 M ) produce nucleosynthesis yields which are in conflict with observationally inferred primordial abundances. Only when this small-scale structure is absent or suppressed, and the collapse efficiency of overdense regions is high, can there exist a range of fluctuation spectral characteristics which concievably could meet all primordial abundance constraints. Even then, the primordial abundance of Li would have to be larger than Li/H ≈ 3 × 10 . In such models, abundance constraints could be met even when the precollapse baryonic fraction of the closure density is Ω ≈ 0.2 h (h is the Hubble parameter in units of 100 km s Mpc ). Nucleosynthesis in these models is characterized by high H/H and low He mass fraction relative to a homogeneous big bang at a given value of Ω h . A potentially observable signature of these models is the production of intrinsic primordial abundance variations on baryon mass scales up to 10 -10 M . 3 4 7 5 7 7 -10 -2 -1 -1 2 4 2 10 12 ⊙ b b ⊙

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