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.

Many compactifications of higher-dimensional supersymmetric theories have approximate vacuum degeneracy. The associated moduli fields are stabilized by non-perturbative effects which break supersymmetry. We show that at finite temperature the effective potential of the dilaton acquires a negative linear term. This destabilizes all moduli fields at sufficiently high temperature. We compute the corresponding critical temperature which is determined by the scale of supersymmetry breaking, the β-function associated with gaugino condensation and the curvature of the Kähler potential, Tcrit ∼ √m3/2 MP (3/β)3/4 K″-1/4. For realistic models we find Tcrit ∼ 1011 - 1012 GeV, which provides an upper bound on the temperature of the early universe. In contrast to other cosmological constraints, this upper bound cannot be circumvented by late-time entropy production. © 2004 Elsevier B.V. All rights reserved.

Physics at the Large Hadron Collider (LHC) and the International e+e- Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC/ILC Study Group so far is summarized in this report. Possible topics for future studies are outlined. © 2006 Elsevier B.V. All rights reserved.