Neutron diffusion and nucleosynthesis in the Universe with isothermal fluctuations produced by quark-hadron phase transition

Nucleosynthesis in the Universe with isothermal baryon-density fluctuations is investigated. It is shown that neutron diffusion during nucleosynthesis plays an important role. Systematic calculations in the wide ranges of parameters suggest that ${\Omega }_B$=1 is marginally consistent with the light-element abundances (D, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$) if the Hubble constant is as small as $H_0$=45 km ${\mathrm{Mpc}}^{\mathrm{-}1}$ ${\sec }^{\mathrm{-}1}$ or the mean lifetime of neutrons is shorter than 860 sec. Moreover it is found that the abundances of CNO elements in the low-density and neutron-rich region are very small.