Superstring compactification and supersymmetry breaking

We set out conditions which enable gaugino condensation to occur in a compactified supergravity model which may be the low-energy limit of a superstring theory. We then argue that the scales of compactification, of supersymmetry breaking and of gauge symmetry breaking can be dynamically determined by radiative corrections in an effective no-scale supergravity model. The resulting low-energy sector may avoid the cosmological gravitino problem - because the gravitino can decay early enough as not to disturb primordial nucleosynthesis. (orig.)