Type I vacua with brane supersymmetry breaking

We show how chiral type I models whose tadpole conditions have no supersymmetric solution can be consistently defined introducing antibranes with non-supersymmetric world volumes. Ar tree level, the resulting stable non-BPS configurations correspond to tachyon-free spectra, where supersymmetry is broken at the string scale on some (anti)branes but is exact in the bulk, and can be further deformed by the addition of brane-antibrane pairs of the same type. As a result, a scalar potential is generated, that can stabilize some radii of the compact space. This setting has the novel virtue of linking supersymmetry breaking to the consistency requirements of an underlying fundamental theory. (C) 2000 Elsevier Science B.V. All rights reserved.