Branes, orientifolds and chiral gauge theories Original Research Article

We discuss some aspects of the physics of branes in the presence of orientifolds and the corresponding world-volume gauge dynamics. We show that at strong coupling orientifolds sometimes turn into bound states of orientifolds and branes, and give a world-sheet argument for the flip of the sign of an orientifold plane split into two disconnected parts by an NS5-brane. We also describe the moduli space of vacua of N = 2 supersymmetric gauge theories with symplectic and orthogonal gauge groups, and analyze a set of four-dimensional N = 1 supersymmetric gauge theories with chiral matter content using branes.