A Supersymmetric Standard Model of Inflation with Extra Dimensions

We embed the supersymmetric standard model of hybrid inflation based on the next-to-minimal superpotential term $\lambda NH_uH_d$ supplemented by an inflaton term $\kappa \phi N^2$, into an extra-dimensional framework, in which all the Higgs fields and singlets live in the bulk, while all the matter fields live on the brane. All the parameters of the effective 4d model can then be naturally understood in terms of a fundamental (``string'') scale $M_*\sim 10^{13}$ GeV and a brane supersymmetry breaking scale $10^{8}$ GeV, of the same order as the height of the inflaton potential during inflation. In particular the very small Yukawa couplings $\lambda \sim \kappa \sim 10^{-10}$ necessary for the model to solve the strong CP problem and generate the correct effective $\mu$ term after inflation, can be naturally understood in terms of volume suppression factors. The brane scalar masses are naturally of order a TeV while the bulk inflaton mass is naturally in the MeV range sufficient to satisfy the slow roll constraints. Curvature perturbations are generated after inflation from the isocurvature perturbations of the supersymmetric Higgs as discussed in a companion paper.