Entropy generation and inflation in wave collision induced pre-big-bang cosmology

We study inflation and entropy generation in a recently proposed pre-big-ba ng model universe produced in a collision of gravitational and dilaton wave s. It is shown that enough inflation occurs provided the incoming waves are sufficiently weak. We also find that entropy in this model is dynamically generated as the result of the nonlinear interaction of the incoming waves, before the universe enters the phase of dilaton driven inflation. In parti cular, we give the scaling of the entropy produced in the collision in term s of the focusing lengths of the incoming waves. (C) 2000 Elsevier Science B.V. All rights reserved.