On string cosmology with a dilaton potential. I

The problems of flat directions and supersymmetry breaking are fundamental problems that are still unsolved in the comparison of string theory with low-energy physics. A possible nonperturbative dilaton potential may play an important role in their solution. In the present paper we consider D-dimensional, low-energy, string cosmological models with a di/aton potential. Exact solutions are written for several simple potentials. The picture of cosmological evolution of a gravi-dilaton model is investigated by methods of the qualitative theory of dynamical systems for different cases of the behavior of the potential in the domain of strong coupling. Features of models having potentials that take negative values in certain ranges of values of the dilaton field are discussed. A specific mechanism of generation of a nonperturbative potential, based on gaugino condensation in the hidden sector of the gauge group, is considered.