A lemon billiard is a planar billiards system whose table is the intersection of two disks with overlapping interiors and two distinct boundary-intersection points. Its boundary consists of two circular arcs meeting at corners. The table is strictly convex, but its boundary is not smooth at those corners.
Fan and Hasselblatt (2026) proved that sufficiently asymmetric lemon billiards have the Bernoulli property, and hence are ergodic. The construction supplies strictly convex ergodic billiards, not examples with a smooth strictly convex boundary.
