Did the Universe Start at Zero Metallicity?

Abstract

Standard Big Bang nucleosynthesis predicts an essentially zero primordial metallicity. I speculate on possible metal (i.e. nucleon number {$}A{\}ge 12{$} ) production in scenarios of inhomogeneous Big Bang nucleosynthesis. It is conceivable, though not necessarily probable, that some primordial metallicity is synthesized if a small fraction of all cosmic baryons reside in very high-density regions. Such conditions could possibly result from the evaporation of some baryon-number carrying soliton prior to the epoch of Big Bang nucleosynthesis.