Modular invariant formulation of multi-gaugino and matter condensation

Using the linear multiplet formulation for the dilaton superfield, we construct an effective Lagrangian for hidden sector gaugino condensation in string effective field theories with arbitrary gauge groups and matter. Non-perturbative string corrections to the Kaehler potential are invoked to stabilize the dilaton at a supersymmetry breaking minimum of the potential. When the cosmological constant is tuned to zero the moduli are stabilized at their self-dual points, and the vevs of their F-component superpartners vanish. Numerical analyses of one- and two-condensate examples with massless chiral matter show considerable enhancement of the gauge hierarchy with respect to the E8 case. The non-perturbative string effects required for dilaton stabilization may have implications for gauge coupling unification. As a comparison, we also consider a parallel approach based on the commonly used chiral formulation. (orig.)