Title: Stability and instability in incompressible fluids Speaker: Michele Coti Zelati Abstract: The study of stability of coherent structures in fluid flows dates back to the late 19th century and has fascinated mathematicians since Reynolds' famous experiments in 1883. Mathematically, this problem can be phrased in terms of estimating the size of the basin of attraction of steady states of the Navier-Stokes equations and related models. In Part I, I will review the theory of stability for shear flows, introducing the concepts of mixing, inviscid damping, and enhanced dissipation. We […]

14.00 - 14.45 : François Thilmany (KU Leuven) « Finding ping-pong partners for finite subgroups of linear groups » In his paper on free subgroups of linear groups, Tits proved his famous alternative: a linear group is either virtually solvable, or contains a free subgroup. Since then, Tits’ work has been generalized and applied in many different ways. One remaining open question in this subject is the one asked by de la Harpe and his collaborators: let $G$ be a semisimple Lie group without compact factors and with trivial center, and let $\Gamma$ […]