Symplectic invariants of semitoric systems and the inverse problem for quantum systems

Abstract

Simple semitoric systems were classified about ten years ago in terms of a collection of invariants, essentially given by a convex polygon with some marked points corresponding to focus--focus singularities. Each marked point is endowed with labels which are symplectic invariants of the system. We will review the construction of these invariants, and explain how they have been generalized or applied in different contexts. One of these applications concerns quantum integrable systems and the corresponding inverse problem, which asks how much information of the associated classical system can be found in the spectrum. An approach to this problem has been to try to compute invariants in the spectrum. We will explain how this has been recently achieved for some of the invariants of semitoric systems, and discuss an open question in this direction.

The height invariant of a four-parameter semitoric system with two focus-focus singularities

“…However, in order for the results to be valid after quantisation, it is important that this classsification preserves the symplectic structure, cf. Pelayo [24] for more details on this approach.…”