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Wednesday, April 5, 2006

**Abstract:** I will start with T-duality, which says that the string compactified on a circle of radius R is equivalent to the string compactified on a circle of radius 1/R in string units. This is extended to mirror symmetry, which identifies the "stringy geometry" of topologically distinct Calabi-Yau manifolds. This leads to a simple method for computing Gromov-Witten invariants of the quintic threefold.