Did the Universe start at Zero Metallicity?

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.Comment: 4 pages, to appear in proceedings of The First Stars meeting, held in Garching, Germany, August 199

Cosmological Deuterium Production in Non-Standard Scenarios

It is widely believed that the cosmic baryon density may be obtained by inferring deuterium abundances in low-metallicity quasar absorption line systems. The implicit assumptions which enter this argument are critically assessed. In particular, the production of deuterium in non-standard Big Bang nucleosynthesis scenarios, the putative production of deuterium in astrophysical environments, and the possible destruction of deuterium via non-standard chemical evolution are discussed.Comment: 11 pages, article based on a talk presented at "Deuterium in the Universe", Meudon, June 2001, to be published in Planetary and Space Scienc

B-ball Dark Matter and Baryogenesis

It has been recently suggested that stable, supersymmetric B-balls formed in the early universe could not only be the dark matter at the present epoch, but also be responsible for baryogenesis by their partial evaporation at high temperatures. We reinvestigate the efficiency of B-ball baryogenesis and find it to be limited by the diffusion of baryon number away from the B-balls. Successful baryogenesis may only occur for B-balls with charges Q\simle 10^{20} - 5\times 10^{23}, which is close to the observational lower limits on the Q of a significant B-ball dark matter component. We also present some cosmological constraints on the abundances of larger B-balls in the early universe.Comment: published version, minor changes and reference adde

Baryon Number Transport in a Cosmic QCD-Phase Transition

We investigate the transport of baryon number across phase boundaries in a putative first order QCD-phase transition. Two independent phenomenological models are employed to estimate the baryon penetrability at the phase boundary: chromoelectric flux tube models; and an analogy to baryon-baryon coalescence in nuclear physics. Our analysis indicates that baryon transport across phase boundaries may be order of magnitude more efficient than other work has suggested. We discuss the substantial uncertainties involved in estimating baryon penetrability at phase boundaries.Comment: 25 pages, 4 figures (available upon request by mail or fax), plain tex, UCRL-JC-00000