N=1 no-scale supergravity from IIB orientifolds

We describe the low-energy effective theory of N=1 spontaneously broken supergravity obtained by flux-induced breaking in the presence of n D3-branes. This theory can be obtained by integrating out three massive gravitino multiplets in the hierarchical breaking N=4→3→2→1 of a N=4 orientifold. This integration also eliminates the IIB complex dilaton. The resulting theory is a no-scale supergravity model, whose moduli are the three chiral multiplets that correspond to the three radii of T2×T2×T2 in T6, together with the 6n brane coordinates. The U(n) gauge interactions on the branes respect the no-scale structure, and the N=1 goldstino is the fermionic partner of the T6 volume.