Dilaton stabilization in effective type I string models

We show that the dilaton and T-moduli can be stabilized by a single gaugino condensation mechanism in the four-dimensional effective field theory derived from type IIB orientifolds. A crucial role is played by the mixing of the blowing-up modes Mk with the T-moduli in the Kahler metric, and by the presence of the Mk in the gauge kinetic functions. Supersymmetry breaking in these models is dominated by the auxiliary fields of the T-moduli, and phenomenologically interesting patterns can emerge. (C) 2001 Elsevier Science B.V. All rights reserved.