Superstring cosmology for N_4 = 1 -> 0 superstring vacua

We study the cosmology of perturbative superstring theory during the radiation(-like) era for semi-realistic backgrounds with initial N=1 supersymmetry. This analysis is necessary for studying the electroweak phase transition within the framework of perturbative string cosmology, and is valid for times after the inflation era (or alternatively Hagedorn era) but before the electroweak symmetry breaking transition. We find that previous results for the N=2 case generalize; namely an attraction to a radiation-like era with the ratio of the supersymmetry breaking scale to temperature stabilized. This provides a dynamical mechanism for setting the supersymmetry breaking scale and its corresponding hierarchy with the Planck scale. For the internal space, we find that both toroidal and orbifold directions never decompactify, except for special cases where toroidal cycles are wrapped by supersymmetry breaking fluxes. This suggests a mechanism for generating spatial directions during the radiation-like era.