2,759 research outputs found

    Gauge Couplings at High Temperature and the Relic Gravitino Abundance

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    In higher-dimensional supersymmetric theories gauge couplings of the effective four-dimensional theory are determined by expectation values of scalar fields. We find that at temperatures above a critical temperature T∗T_*, which depends on the supersymmetry breaking mass scales, gauge couplings decrease like T^{-\a}, \a > 1. This has important cosmological consequences. In particular it leads to a relic gravitino density which becomes independent of the reheating temperature for TR>T∗T_R > T_*. For small gravitino masses, m_{3/2} \ll m_{\gl}, the mass density of stable gravitinos is essentially determined by the gluino mass. The observed value of cold dark matter, \O_{\rm CDM}h^2 \sim 0.1, is obtained for gluino masses m_{\gl} = {\cal O}(1 {\rm TeV}).Comment: 11 pages, 2 figures, comment on supersymmetry breaking mechanisms and two references adde

    Heat Transfer Characteristics of Regenerator Matrix (Case of Packed Wire Gauzes)

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    The average heat transfer coefficient in the matrix of laminated wire screens (10 to 250 mesh) for a Stirling engine heat exchanger was studied experimentally. The data are correlated by N sub ud = 0.42 R sub ed 0.56 (3 or = R sub ed or = 400), and R sub ed are the Nusselt and Reynolds nubmers based on the wire diameter. The pressure drop decreased and the heat transfer increased as the wire diameter was decreased

    Variations on Supersymmetry Breaking and Neutrino Spectra

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    The problem of generating light neutrinos within supersymmetric models is discussed. It is shown that the hierarchy of scales induced by supersymmetry breaking can give rise to suppression factors of the correct order of magnitude to produce experimentally allowed neutrino spectra.Comment: 18 pages, LaTeX, Contribution to "Neutrino Workshop", Fuji-Yoshida, Japan, August 200
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