11:00 Georgios Dimitroglou Rizell (Orsay)
Exotic spheres and the topology of the symplectomorphism group.
Abstract: We show that the Hamiltonian isotopy class of the symplectic Dehn twist depends on the parametrisation used in the construction. Moreover, this result is used to construct non-trivial symplectomorphisms of T^*(S^n x S^1) having compact support, as well as non-standard symplectic structures on T^*(S^n x S^1) coinciding with the standard structure outside of a compact set. Joint work with Jonny Evans.
14:15 Dmitri Panov (London)
Circle invariant fat bundles and symplectic Fano 6-manifolds
Abstract : Let E be an SO(3) bundle over a four manifold M. A metric connection A in E is called fat or definite, if F_A(u,v) is non-zero whenever u,v are linearly independent tangent vectors. It will discuss the following result obtained with Joel Fine:
Theorem: If a closed 4-manifold M admits an S1-invariant definite connection then M is diffeomorphic to either S 4 or CP 2. I will explain how this result is related to symplectic geometry, and to positively curved manifolds.
16:00 Vinicius Gripp Ramos (Nantes)
Embedded contact homology and symplectic embeddings.
Prochaine séance: début octobre!