4:00 pm Thursday, October 1, 2015

Rich Schwartz (Brown)

Abstract: Outer billiards is a dynamical system that is
similar in spirit to ordinary billiards, except that the
ball moves around the outside of the table.
Even for simple tables, such as kites
(quadrilaterals with bilateral symmetry)
the orbits produced have a rich combinatorial
structure. I'll describe a combinatorial model, which I call
the plaid model, which predicts the shapes of these orbits
for kites. The model involves mathematics which is similar
in spirit to what one sees for quasi-periodic tilings.