Some questions concerning the low-energy limit of superstring theories

Certain classical symmetries in superstring theories prevent us from understanding some relevant parameters like the magnitude of gauge coupling constants and the compactification scale. Resulting low-energy approximations are therefore not unambiguously defined. The authors investigate the breakdown of these symmetries and clarify which properties of the low-energy theory are artifacts of the classical approximation. Such a discussion has consequences for the relation between gauge coupling constants and the magnitude of the supersymmetry breakdown scale