Title: Measures on differentiable stacks
Abstract: This talk is based on a joint paper with Joao Nuno Mestre, with the same title. I will discuss measures and densities (= geometric measures) on differentiable stacks, using a rather straightforward generalization of Haefliger's approach to leaf spaces and to transverse measures for foliations. The concepts we are proposing are also compatible with the idea of measure from non-commutative geometry and Weinstein's approach to "the volume of a differentiable stack". In the proper case, the resulting measures can be seen as classical (Radon) measures on the underlying orbispace; actually, the main motivation for this work is the case of proper symplectic groupoids that are central to our approach to compactness in Poisson geometry- that is, the PMCT-project, joint with Rui Fernandes and David Martinez Torres.