UC Irvine

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*, which depends on the supersymmetry breaking mass scales, gauge couplings decrease like T-α, α > 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*. For small gravitino masses, m3/2 ≪ mg̃, the mass density of stable gravitinos is essentially determined by the gluino mass. The observed value of cold dark matter, ΩCDMh2 ∼ 0.1, is obtained for gluino masses mg̃ = script O sign (1 TeV). © 2003 Published by Elsevier B.V.