Dilaton Stabilization and Supersymmetry Breaking by Dynamical Gaugino Condensation in the Linear Multiplet Formalism of String Effective Theory

We study dynamical gaugino condensation in superstring effective theories using the linear multiplet representation for the dilaton superfield. An interesting necessary condition for the dilaton to be stabilized, which was first derived in generic models of static gaugino condensation, is shown to hold for generic models of dynamical gaugino condensation. We also point out that it is stringy non-perturbative effects that stabilize the dilaton and allow dynamical supersymmetry breaking via the field-theoretical non-perturbative effect of gaugino condensation. As a typical example, a toy S-dual model of a dynamical E_8 condensate is constructed and the dilaton is explicitly shown to be stabilized with broken supersymmetry and (fine-tuned) vanishing cosmological constant.