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\geq 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.