Dilaton stabilization in effective type I string models

Abstract We show that the dilatonand T - modulican be stabilized by a single gaugino condensationmechanism in the four-dimensional effective field theoryderived from type IIB orientifolds. A crucial role is played by the mixing of the blowing-upmodes M k with the T - moduliin the Kahler metric, and by the presence of the M k in the gauge kinetic functions. Supersymmetry breakingin these models is dominated by the auxiliary fieldsof the T - moduli, and phenomenologically interesting patterns can emerge.