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Characteristic polynomials and dilatations of pseudo-Anosov mapping classes 

4:00 pm Thursday, November 4, 2010
Joan Birman (Columbia University)

The mapping class group of a 2-manifold S, known as Mod(S), is the group of orientation-preserving diffeomorphisms of S, modulo those diffeomorphisms that are isotopic to the identity. We will review some of the developments that followed after William Thurston's discovery, in 1976, of a striking new way to think about elements in Mod(S). We will discuss recent work that relates to the "dilatation" of certain elements in Mod(S). It's a real number, and it's a conjugacy class invariant.

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