Open-closed string duality from orbifolded conifolds

We study large N   dualities for a class of N=1 theories realized on type IIB D5 branes wrapping two-cycles of local Calabi-Yau three-fold which is obtained from resolving orbifolded conifolds or as effective field theories on D4 branes in type IIA brane configurations. The field theory is N=1 supersymmetric ∏U(Nij)∏U(Nij) Yang-Mills gauge theory. Strong coupling effects are analyzed in the deformed geometry. We propose closed string duality via a geometric transition in toric geometry. The T-dual type IIA picture and M-theory lifting are also considered.