Open Problems on Billiards and Geometric Optics

Examples of projective billiards with open sets of periodic orbits

“…Knowing these examples, many questions arise: are there polygonal examples of n-reflective projective billiards with n ≥ 5 odd (see [3] for more details)? Can we find centrally-projective billiards which are n-reflective but not built on polygons?…”