Activities This Week
BGU Probability and Ergodic Theory (PET) seminar
Allosteric actions of surface groups Online
Nov 11, 11:10—12:00, 2021, -101
Speaker
Matthieu Joseph (École normale supérieure de Lyon)
Abstract
In a recent work, I introduced the notion of allosteric actions: a minimal action of a countable group on a compact space, with an ergodic invariant measure, is allosteric if it is topologically free but not essentially free. In the first part of my talk I will explain some properties of allosteric actions, and their links with Invariant Random Subgroups (IRS) and Uniformly Recurrent Subgroups (URS). In the second part, I will explain a recent result of mine: the fundamental group of a closed hyperbolic surface admits allosteric actions.
Non-commutative Analysis Seminar
On Operators In The Cowen-Douglas Class And Homogeneity (part 1)
Nov 15, 14:30—16:00, 2021, -101
Speaker
Prahllad Deb (BGU)
Colloquium
Big Fiber Theorems and Ideal-Valued Measures in Symplectic Topology
Nov 16, 14:30—15:30, 2021, Math -101
Speaker
Yaniv Ganor (Technion)
Abstract
In various areas of mathematics there exist “big fiber theorems”, these are theorems of the following type: “For any map in a certain class, there exists a ‘big’ fiber”, where the class of maps and the notion of size changes from case to case.
We will discuss three examples of such theorems, coming from combinatorics, topology and symplectic topology from a unified viewpoint provided by Gromov’s notion of ideal-valued measures.
We adapt the latter notion to the realm of symplectic topology, using an enhancement of a certain cohomology theory on symplectic manifolds introduced by Varolgunes, allowing us to prove symplectic analogues for the first two theorems, yielding new symplectic rigidity results.
Necessary preliminaries will be explained. The talk is based on a joint work with Adi Dickstein, Leonid Polterovich and Frol Zapolsky.
AGNT
TBA
Nov 17, 16:00—17:15, 2021, -101
Speaker
No talk
Abstract
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