Resumen de Global hamiltonian dynamics on singular symplectic manifolds
Cedric Oms
n this thesis, we study the Reeb and Hamiltonian dynamics on singular symplectic and contact manifolds. Those structures are motivated by singularities coming from classical mechanics and fluid dynamics.
We start by studying generalized contact structures where the non-integrability condition fails on a hypersurface, the critical hypersurface. Those structures, called $b$-contact structures, arise from hypersurfaces in $b$-symplectic manifolds that have been previously studied extensively in the past. Formerly, this odd-dimensional counterpart to $b$-symplectic geometry has been neglected in the existing vast literature. Examples are given and local normal forms are proved. The local geometry of those manifolds is examined using the language of Jacobi manifolds, which provides an adequate set-up and leads to understanding the geometric structure on the critical hypersurface. We further consider other types of singularities in contact geometry, as for instance higher order singularities, called $b^m$-contact forms, or singularities of folded type.
Obstructions to the existence of those structures are studied and the topology of $b^m$-contact manifolds is related to the existence of convex contact hypersurfaces and further relations to smooth contact structures are described using the desingularization technique.
We continue examining the dynamical properties of the Reeb vector field associated to a given $b^m$-contact form. The relation of those structures to celestial mechanics underlines the relevance for existence results of periodic orbits of the Hamiltonian vector field in the $b^m$-symplectic setting and Reeb vector fields for $b^m$-contact manifolds. In this light, we prove that in dimension $3$, there are always infinitely many periodic Reeb orbits on the critical surface, but describe examples without periodic orbits away from it in any dimension. We prove that there are traps for this vector field and discuss possible extensions to prove the existence of plugs. We will see that in the case of overtwisted disks away from the critical hypersurface and some additional conditions, Weinstein conjecture holds: more precisely there exists either a periodic Reeb orbit away from the critical hypersurface or a $1$-parametric family in the neighbourhood of it. The mentioned results shed new light towards a singular version for this conjecture.
The obtained results are applied to the particular case of the restricted planar circular three body problem, where we prove that after the McGehee change, there are infinitely many non-trivial periodic orbits at the manifold at infinity for positive energy values.
