Vadim Kaloshin

Pennsylvania State University; Member, School of Mathematics, Institute for Advanced Study

January 25, 2012

There are indications that in the 80s Guillemin posed a question: If billiard maps are conjugate, can we say that domains are the same up to isometry?

On one side, we show that conjugacy of different domains can't be C^1 near the boundary. In particular, billiard maps of the circle and an ellipse are both analytically integrable, but not C^1 conjugate. On the other side, if conjugate near the boundary s smoother, then domains are the same up to isometry.

(This is joint work with A. Sorrentino.)