Regular cosmological examples of tree-level dilaton-driven models

We construct analytic solutions of the low energy (i.e., tree-level) string cosmological effective action. We work with the "minimal" field content (i.e.; graviton and dilaton) in the absence of any dilaton potential and of any antisymmetric tensor field. Provided the metric is sufficiently inhomogeneous we obtain solutions whose curvature invariants are bounded and everywhere defined in time and space. The dilaton coupling and its associated energy density are regular and homogeneous. A phase of growing (and nonsingular) dilaton coupling is compatible with the regularity of the curvature invariants without the addition of higher curvature (or higher genus) corrections to the tree-level effective action. We discuss the symmetries and the physical properties of the obtained solutions.