A note on brane boxes at finite string coupling

We consider N=1 supersymmetric SU(Nc) gauge theories, using the type IIB brane construction recently proposed by Hanany and Zaffaroni. At non-zero string coupling, we find that the bending of branes imposes consistency conditions that allow only non-anomalous gauge theories with stable vacua, i.e., Nf≥Nc, to be constructed. We find qualitative differences between the brane configurations for Nf≤3Nc and Nf>3Nc, corresponding to asymptotically free and infrared free theories respectively. We also discuss some properties of the brane configurations that may be relevant to constructing Seibergʹs duality in this framework.