In this talk, we first introduce the notion of a *continuous cover* of a manifold parametrised by any compact manifold endowed with a mass 1 volume-form. We prove that any such cover admits a partition of unity where the usual sum is replaced by integrals. We then generalize Polterovich's notion of Poisson non-commutativity to such a context in order to get a richer definition of non-commutativity and to be in a position where one can compare various invariants of symplectic manifolds, for instance the relation between critical values of phase transitions of symplectic balls and eventual critical values of the Poisson non-commutativity. Our first main theorem states that our generalisation of Poisson non-commutativity depends only on real one-parameter spaces since intuitively the Hilbert curve in any high dimensional parameter space fills out the entire manifold and preserves the measure. Our second main theorem states that the Poisson non-commutativity is a (not necessarily strictly) decreasing function of the size of the symplectic balls used to cover continuously any given symplectic manifold. This function has other nice properties as well that do not prevent it from undergoing singularities similar to phase transitions. Joint work with Jordan Payette with a major input by Lev Buhovsky.

# Continuous covers on symplectic manifolds

François Lalonde

University of Montreal

March 24, 2017