The Fomenko–Zieschang invariants of nonconvex topological billiards

Along with a classical planar billiard, one can consider a topological billiard for which the motion takes place on a locally planar surface obtained by an isometric gluing of several planar domains along boundaries that are arcs of confocal quadrics. Here, a point is moving inside every domain along segments of straight lines, passing from one domain into another when it hits the boundary of the gluing. The author has previously obtained the Liouville classification of all such topological billiards obtained by gluings along convex boundaries. In the present paper, we classify all topological integrable billiards obtained by gluing both along convex and along nonconvex boundaries from elementary billiards bounded by arcs of confocal quadrics. For all such nonconvex topological billiards, the Fomenko–Zieschang invariants (marked molecules $W^*$) of Liouville equivalence are calculated.
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