S-brane to thermal non-singular string cosmology

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We present a new class of non-singular string cosmologies in d space-time dimensions. At very early times, τ<< τc, the Universe is described by a flat σ-model metric, a constant maximal temperature Tc and super-weak string interactions, gₛtr << 1. During the evolution, the metric remains flat up to τc, while the string coupling grows and reaches a critical value g*ₛtr at τc. This phase is characterized by a uniform temporal distribution of spacelike branes. At later times, τ> τc, the Universe enters in a new phase of expansion, with radiation. The string coupling decreases due to the dilaton motion and asymptotes to a constant for τ>> τc. Throughout the evolution, the string coupling remains smaller than g*ₛtr. In the Einstein frame, the cosmologies describe bouncing Universes, where two distinct phases are connected at τc. In the initial contracting phase, the evolution of the scale factor is identical to that of a negatively curved Universe filled with radiation. At later times, the Universe enters in an expanding thermal phase with a running dilaton. Explicit examples are presented in a large class of thermal (4,0) type II superstring vacua, with non-trivial "gravito-magnetic" fluxes.