$C^\infty$ symplectic invariants of parabolic orbits and flaps in integrable Hamiltonian systems

Abstract

In the present paper, we consider a smooth $C^\infty$ symplectic classification of Lagrangian fibrations near cusp singularities, parabolic orbits and cuspidal tori. We show that for these singularities as well as for an arrangement of singularities known as a flap, which arises in the integrable subcritical Hamiltonian Hopf bifurcation, the action variables form a complete set of $C^\infty$ symplectic invariants. We also give a symplectic classification for parabolic orbits in the real-analytic case. Namely, we prove that a complete symplectic invariant in this case is given by a real-analytic function germ in two variables. Additionally, we construct several symplectic normal forms in the $C^\infty$ and/or real-analytic categories, including real-analytic right and right-left symplectic normal forms for parabolic orbits.