Abstract:We clarify some ambiguous points in a derivation of duality via brane exchange using M-theory language, and propose a “proof” of duality in MQCD. Actually, duality in MQCD is rather trivial and does n...We clarify some ambiguous points in a derivation of duality via brane exchange using M-theory language, and propose a “proof” of duality in MQCD. Actually, duality in MQCD is rather trivial and does not need a complicated proof. The problem is how to interpret it in field theory language. We examine BPS states in theory and find the particle correspondence under duality. In the process, we also find some exotic particles in MQCD, and we observe an interesting phenomenon in type IIA string theory, namely, that fundamental strings are converted into D2-branes via the exchange of two NS5-branes. We also discuss how we should understand Seiberg's duality from exact duality in MQCD.Read More