Combining the baryon budget with cosmic microwave background radiation measurements |
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Authors: | S. Hannestad |
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Affiliation: | Institute of Physics and Astronomy, University of Aarhus, DK-8000 Århus C, Denmark |
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Abstract: | Measurements of the cosmic microwave background radiation (CMBR) provide a powerful tool with which to measure the primary cosmological parameters. However, there is a large degree of parameter degeneracy in simultaneous measurements of the matter density, Ωm, and the Hubble parameter, H 0. In the present paper we use the currently available CMBR data together with measurements of the cosmological baryon-to-photon ratio, η , from big bang nucleosynthesis, and the relative mass fraction of baryons in clusters to break the parameter degeneracy in measuring Ωm and H 0. We find that present data are inconsistent with the standard Ω=1, matter-dominated model. Our analysis favours a medium-density universe with a rather low Hubble parameter. This is compatible with new measurements of Type Ia supernovae, and the joint estimate of the two parameters is and . We stress that the upper bound on the Hubble parameter is likely to be much more uncertain than indicated here, because of the limited number of free parameters in our analysis. |
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Keywords: | cosmic microwave background dark matter |
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