Outer billiards outside regular dodecagon: computer proof of periodicity of almost all orbits and existence of an aperiodic point

Abstract

An existence of an aperiodic point for outer billiard outside regular dodecagon is proved. Additionally, almost all orbits of such an outer billiard are proved to be periodic, and all possible periods are listed explicitly. The proof is based on facts established with computer program implemented by author. All calculations of a program has been made with absolute accuracy; these calculations can be done "by hands" but it this case, amount of calculations would be too large.