Dr Cezar Condeescu (CPHT - Ecole Polytechnique)
We investigate the transmutation of D-branes into Abelian magnetic backgrounds on the world-volume of higher-dimensional branes, within the framework of global models with compact internal space. The phenomenon, T-dual to brane recombination in the intersecting-brane picture, shares some similarities to small-instanton transitions in non-compact space, though in this case the Abelian magnetic background is a consequence of the compactness of the internal manifold, and is not ascribed to a zero-size non-Abelian instanton growing to maximal size. We study the similarities and differences between the two cases in the supersymmetric case. We provide details of the transition in various supersymmetric and non-supersymmetric tachyon-free orientifold with Brane Supersymmetry Breaking, both from brane recombination and from field theory Higgsing viewpoints. The Higgs mechanism is ignited by non-vanishing vev's for D7-D7' scalars, as in the small instanton transitions.