Billiards and Geometric Topology

Moon Duchin
Department of Mathematics, UC Davis

Abstract: Geometry is topology plus extra structure—notions like angle, distance, and curvature. In the case of surfaces, you might ask about all the different ways to metrize a given topological surface. If you were really demanding, you might ask for a way of measuring how different two metrics are from each other: you'd be asking for a metric on the space of metrics. It turns out that this is a reasonable demand to make, and that one good answer comes from so-called flat structures—a generalization of billiard tables.