Cosmology of supersymmetric models with low-energy gauge mediation

Abstract

We study the cosmology of supersymmetric models in which the supersymmetry breaking effects are mediated by gauge interactions at about the 10 5 GeV scale. We first point out that the gravitino is likely to overclose the Universe in this class of models. This requires an entropy production, which prefers a baryogenesis mechanism at a relatively low temperature. The Affleck-Dine mechanism for baryogenesis is one of the possibilities to generate enough baryon asymmetry, but the analysis is non-trivial since the shape of the potential for the flat direction differs substantially from the conventional hidden sector case. To see this, we first perform a 2-loop calculation to determine the shape of the potential. By combining the potential with the supergravity contribution, we then find that the Affleck-Dine baryogenesis works efficiently to generate sufficient baryon asymmetry. On the other hand, we also point out that string moduli fields, if present, are stable and their coherent oscillations overclose the Universe by more than 15 orders of magnitude. One needs a very late inflationary period with an e-folding of N > ∼ 5 and an energy density of < ∼ (10 7 GeV) 4 . A thermal inflation is enough for this purpose. Fortunately, the Affleck-Dine baryogenesis is so efficient that enough baryon asymmetry can survive the late inflation. * This work was supported in part by the

The soft supersymmetry-breaking Lagrangian: theory and applications

“…This may cause problems in the context of gauge mediation [23,558,559], because such low values for the F term are unattractive in some gauge-mediated models. One may need to invoke methods to dilute the gravitino abundance [560] or have a low reheating temperature [558,559]. In certain special arrangements of the sparticle mass spectrum, there can be a secondary population of nonthermal gravitinos from NLSP decay [561].…”

Thermodynamics of non-topological solitons

“…The MSSM with unbroken supersymmetry has a lot of gauge invariant flat directions with V (φ) = 0 carrying baryon number [4]. If supersymmetry is broken at a low energy scale M, as in gauge-mediated scenarios [5], then the potential is lifted at φ > M in a way that V (φ) stays constant [6,7]. Thus, this theory contains stable non-topological solitons which carry baryon number [8].…”

Exponentially small supersymmetry breaking from extra dimensions

“…Note that this is truly a model of low-energy supersymmetry breaking, with √ F ∼ 16π 2 m ∼ 100 TeV, allowing for decays of the NLSP within a detector length. Moreover, this small value for √ F is favored by cosmology in that it suppresses the gravitino energy density [10]. Depending on whether supersymmetric or supersymmetry-breaking stabilization of the radius is employed, the radion mass is either m radion ∼ M 2 * /M P or m radion ∼ √ F /M P ∼ 1 eV (M * /M P ).…”