Issues on orientifolds: On the brane construction of gauge theories with SO(2n) global symmetry

Abstract

We discuss issues related to orientifolds and the brane realization for gauge theories with orthogonal and symplectic groups. We specifically discuss the case of theories with (hidden) global SO(2n) symmetry, from three to six dimensions. We analyze mirror symmetry for three dimensional N=4 gauge theories, Brane Box Models and six-dimensional gauge theories. We also discuss the issue of T-duality for Dn space-time singularities. Stuck D branes on ON0 planes play an interesting role.