Cosmological solutions in string theories
Additional Document Info
We obtain a large class of cosmological solutions in the toroidally compactified low-energy limits of string theories in [Formula presented] dimensions. We consider solutions where a [Formula presented]-dimensional subset of the spatial coordinates, parametrizing a flat space, a sphere, or a hyperboloid, describes the spatial sections of the physically observed Universe. The equations of motion reduce to Liouville or SL[Formula presented] Toda equations, which are exactly solvable. We study some of the cases in detail, and find that under suitable conditions they can describe four-dimensional expanding universes. We discuss also how the solutions in [Formula presented] dimensions behave upon oxidation back to the [Formula presented] string theory or [Formula presented] [Formula presented] theory. 1997 The American Physical Society.