I will study the dynamics of a class of orientifold constructions where supersymmetry is classically exact in bulk but it is explicitly broken on the branes at the string scale. Using S and T dualities, I will show how these non-supersymmetric models can be interpreted as metastable vacua of type I superstring. This dynamics can also be captured by the nucleation of brane-antibrane pairs and subsequent tachyon nucleation.

INFN Turin