A family of semitoric systems with four focus-focus singularities and two double pinched tori

Annelies De Meulenaere, Sonja Hohloch

We construct a 1-parameter family $F_t=(J,H_t{)}_{0\le t\le 1}$ of integrable systems on a compact $4$-dimensional symplectic manifold $(M,\omega )$ that changes smoothly from a tori…