We present a detailed numerical study of inhomogeneous big bang nucleosynthesis where, for the first time, nuclear reactions are coupled to all significant fluctuation dissipation processes. These processes include neutrino heat transport, baryon diffusion, photon diffusive heat transport, and hydrodynamic expansion with photon-electron Thomson drag. Light-clement abundance yields are presented for broad ranges of initial amplitudes and length scales for spherically condensed fluctuations. The 2H, 3He, 4He, and 7Li nucleosynthesis yields are found to be inconsistent with observationally inferred primordial abundances for all but very narrow ranges of fluctuation characteristics. Rapid hydrodynamic expansion of fluctuations late in the nucleosynthesis epoch results in significant destruction of 7Li (7Be) only if the baryonic contribution to the closure density (Ωb) is less than or comparable to the upper limit on this quantity from homogeneous big bang nucleosynthesis. This implies that 7Li overproduction will preclude an increase on the upperlimit for Ωb for any inhomogeneous nucleosynthesis scenario employing spherically condensed fluctuations.

We investigate the recently observed periodicity of the distribution of galaxies at high redshift by comparing the data with models in which galaxies reside on the surfaces of bubbles or sheets. A statistical analysis of the deviation from periodicity along various lines of sight seems to suggest that the data more closely resemble a regular cellular pattern in which the bubble centers are strongly anticorrelated than a distribution produced by random voids or sheets. We discuss how such a regular structure might arise and suggest some observational tests of this interpretation.

We study several models for the origin and chemical evolution of compact irregular galaxies in order to determine the primordial 4He abundance, Yp, from the zero metallicity intercept of the observed Y versus Z correlations. This study confirms the suggestion that a straight-line fit to the observations does not necessarily give the correct primordial 4He abundance. This is especially true for the extrapolation of the Y versus N/H data which depends upon the relative contributions from secondary and primary nitrogen in low metallicity stars. The extrapolation of the O/H data is also slightly nonlinear even for primary oxygen in a closed-box model with instantaneous recycling due to the time dependence of the hydrogen mass fraction, the breakdown of the instantaneous recycling approximation, the production of helium, nitrogen, and oxygen in stars of different mass, and ejection of metal-poor material from low-mass stars. Our best fits to the data, even after excluding possible contamination of H II regions from neighboring Wolf-Rayet stars, gives Yp = 0.228 ± 0.005 for O/H and Yp = 0.223 ± 0.006 for N/H. These primordial helium abundances are as much as 2 σ below the minimum helium abundance which can be produced in the standard homogeneous big bang model with three light neutrino flavors. This discrepancy may be due to shortcomings of the chemical evolution models, additional systematic errors in the determination of the helium and/or metal abundances in extragalactic H II regions, or effects of nonstandard primordial nucleosynthesis.

We discuss the primordial nucleosynthesis of intermediate-mass nuclei up to A = 28 in the neutron-rich and proton-rich environments produced by baryon-number-inhomogeneous big bang models. We find that there could be several observational signatures of such neutron-rich and proton-rich primordial nucleosynthesis if sufficiently accurate isotopic and elemental abundance ratios could be measured for extremely metal-poor stars. These observations could also provide important information about the degree of baryon-number inhomogeneity at the time of primordial nucleosynthesis.

Primodial nucleosynthesis calculations are shown to be able to provide constraints on models of electroweak baryogenesis which produce a highly inhomogeneous distribution of the baryon-to-photon ratio. Such baryogenesis scenarios overproduce 4He and/or 7Li and can be ruled out henever a fraction f≲3×10-6(100GeV/T)3 of nucleated bubbles of broken-symmetry phase contributes ≳10% of the baryon number within a horizon volume. © 1994.

We study the quark-hadron transition in the early Universe and compute the amplitude of isothermal baryon-number fluctuations that emerge from this transition along with their effects on primordial nucleosynthesis. We find that such fluctuations are a natural consequence of a first-order phase transition occurring in the strongly interacting system. Fluctuation-generating mechanisms are discussed. We estimate the nucleation rate and derive the mean separation between fluctuations. It is shown that the amplitude of the fluctuations depends sensitively on the phase coexistence temperature Tc and on the baryon transmission probability h at the phase boundary. For realistic values of h and Tc the fluctuations are large and have a significant effect on primordial nucleosynthesis yields. With these fluctuations the limit on the baryonic contribution to depends primarily on what is taken to be the primordial Li7 abundance: =1 in baryons would require large Li7 and H2 destruction factors during the evolution of the Galaxy. © 1988 The American Physical Society.

We discuss two scenarios for the galactic chemical evolution of lithium. In one, the primordial 7Li abundance is taken to be that presently observed in Population II stars. This value is subsequently enriched to the Population I value by stellar sources. In the other scenario, the primordial 7Li abundance is taken to be as high as that suggested by baryon number inhomogeneous cosmological models in which the universe is closed with baryons. This value is then depleted to the present-day Population I value by astration. The Population II value is obtained by gradual main-sequence destruction. Our models include the results of new calculations of lithium destruction and production in stars. The models are constrained by observations of deuterium, lithium, and beryllium as a function of galactic age and by the observed lack of correlation between Fe and Li for metal-poor stars. We find that these constraints can be satisfied by either scenario. We discuss the possibility that the recently derived upper limit to the lithium absorption along the line of sight to SN 1987A may provide a means to distinguish between these two scenarios.

A first-order phase transition is likely to have occurred in the early universe at the end of the quark era and the beginning of the hadron era. This phase transition would have created large amplitude isothermal fluctuations in the distribution of baryon number in the universe. These fluctuations have significant impact on the subsequent synthesis of isotopes of hydrogen, helium and lithium out of protons and neutrons. It turns out to be possible that all of the mass in the universe today is baryonic. © 1989.