Dualities in 4D Theories with Product Gauge Groups from Brane Configurations

We study brane configurations which correspond to N=1 field theories in four dimensions. By inverting the order of the NS 5-branes and D6-branes, a check on dualities in four dimensional theories can be made. We consider a brane configuration which yields electric/magnetic duality for gauge theories with $SO(N_{c1})\times Sp(N_{c2})$ product gauge group. We also discuss the possible extension to any alternating product of SO and Sp groups. The new features arising from the intersection of the NS 5-branes on the orientifold play a crucial role in our construction.