Аннотация:
Inspired by the recent results toward Birkhoff conjecture (a rigidity property
of billiards in ellipses), we discuss two rigidity properties of conics. The first one concerns
symmetries of an analog of polar duality associated with an oval, and the second concerns
properties of the circle map associated with an oval and two pencils of lines.
Ключевые слова:conics, polar duality, rigidity, circle maps, chess billiards.