Currently the WMAP results give a baryon:photon ratio of ~6.2x10(adsbygoogle = window.adsbygoogle || []).push({}); ^{-10}, and a dark:baryonic mass ratio of ~5. When added to the energy density of photons + neutrinos (+dark energy at later times), the total density is then critical for a flat Universe. The BB nucleosynthesis analysis of the relative abundance of 4He, D, 3He, and 7Li strongly suggest that the baryon:photon ratio is <4.5x10^{-10}with 4-5 sigmas confidence level (excluding some kind of likely systematic error in 7Li) See figs 3 and 4 of

http://arxiv.org/PS_cache/arxiv/pdf/0808/0808.2818v1.pdf

If the dark:baryonic mass ratio remains ~5, and we believe the 7Li results, this would put the energy density at the CMB last scattering surface at only ~79% of critical. Can this be fixed simply by increasing the dark:baryonic mass ratio, or is there some independent reason the ratio must be 5?

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# Can the Li7 problem be resolved by increasing the dark matter ratio?

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