An M-theory flop as a large N duality

We show how a recently proposed large N duality in the context of type IIA strings with N=1 supersymmetry in 4 dimensions can be derived from purely geometric considerations by embedding type IIA strings in M-theory. The phase structure of M-theory on G(2) holonomy manifolds and an S-3 flop are the key ingredients in this derivation. (C) 2001 American Institute of Physics.