A Model of Anthropic Reasoning, Addressing the Dark to Ordinary Matter Coincidence

Abstract

If inflation occurs after the breaking of Peccei-Quinn symmetry then large values of the breaking scale $F$, which are forbidden in conventional axion cosmology, are permitted, provided that we inhabit a region of the Multiverse where the initial misalignment is small. Regions having approximately this initial misalignment may occupy a small volume of the Multiverse, but they contain a large fraction of potential observers. This scenario has many consequences, including a possible explanation of the approximate equality of dark and baryon matter densities.

arXiv commentSolicited article for the book ``Universe or Multiverse?'', ed. B. Carr, based in part on a talk at the Anthropic Workshop, Cambridge University, June 2001. v2 additional references, minor typos corrected

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