Speaker : Professor Sinisa Slijepcevic (University of Zagreb) Title : New construction of positive entropy invariant measures of twist maps Time : 2018-07-02 (Mon) 15:00 - 16:30 Place : Seminar Room 722, Institute of Mathematics (NTU Campus) Abstract: We introduce a new measure of instability of area preserving twist diffeomorphisms, which generalizes the notions of angle of splitting of separatrices, and flux through a gap of a Cantori. As an example of application, we establish a sharp > 0 lower bound on the topological entropy in a neighbourhood of a hyperbolic, unique action-minimizing fixed point, assuming only no topological obstruction to diffusion, i.e. no homotopically non-trivial invariant circle consisting of orbits with the rotation number 0.