Workshop 1 - Operator Algebras: Groups and Dynamics

Sep 28, 2026, 8:30 AM → Oct 2, 2026, 5:30 PM Europe/Paris

Amphithéâtre Hermite (Institut Henri Poincaré)

Operator Algebras: Approximation, Rigidity and Dynamics.

Workshop 1 - Operator Algebras: Groups and Dynamics

September 28 to October 2, 2026 - IHP, Paris

Summary

The workshop will feature talks on the latest developments on the interaction between operators algebras, group representation theory, group actions, topological dynamics and ergodic theory.

List of speakers:

• Goulnara Arzhantseva 
• Uri Bader 
• Emmanuel Breuillard 
• Pierre-Emmanuel Caprace 
• David Fisher 
• Shirly Geffen 
• Ursula Hamenstädt 
• Adrian Ioana 
• Mehrdad Kalantar 
• Fanny Kassel  
• Corentin Le Bars
• Waltraud Lederle 
• Arie Levit
• Simon Machado 
• Hanna Oppelmayer 
• Denis Osin 
• Sven Raum
• Yehuda Shalom 
• Itamar Vigdorovich 
• Tianyi Zheng

Organising Committee:

• Camille Horbez
• Cyril Houdayer
• Corentin Le Bars 

abstracts_workshop1.pdf

schedule_workshop1.pdf

Mon, September 28

9:30 AM Welcome Coffee/ Badge Distribution

10:00 AM Opening Speech by IHP's Deputy Director, Prof. Mariana Grana

1 Uri Bader: How to get infected with Lp-cohomology and how to cure it?

10:55 AM Coffee break

2 Simon Machado: Quantitative growth of the injectivity radius

12:00 PM Lunch

3 Adrian Ioana: Rigidity for graph product von Neumann algebras

2:45 PM Coffee break

4 Ursula Hamenstädt: Mixing and counting in relatively hyperbolic groups

5 Hanna Oppelmayer: Random subalgebras

Tue, September 29

6 Emmanuel Breuillard: Expander Cayley graphs and non-abelian Littlewood-Offord

10:45 AM Coffee break

7 Tianyi Zheng: Commensurating actions and the Sierpiński carpet group

12:00 PM Group Photo

12:10 PM Lunch

8 Yehuda Shalom: Progress on the Margulis-Zimmer conjecture

2:45 PM Coffee break

9 Goulnara Arzhantseva: Simple and selfless reduced group C*-algebras

10 Corentin Le Bars: Charmenability of twin building lattices

Cocktail

Wed, September 30

11 Pierre-Emmanuel Caprace: Mixing versus amenability for unitary representations of groups acting on buildings

10:15 AM Coffee break

12 Denis Osin: A paradoxical route from hyperbolic geometry to proper proximality

13 Shirly Geffen: Stable rank one in nonnuclear C*-algebras

Thu, October 1

14 Waltraud Lederle: Boomerang subgroups, Schreier graphs and avoiding invariant measures

10:45 AM Coffee break

15 Mehrdad Kalantar: On Invariant Random Subgroups of C*-Simple Groups

12:00 PM Lunch

16 Sven Raum: K-theory and delocalised traces of right-angled Hecke C*-algebras

2:45 PM Coffee break

17 Itamar Vigdorovich: Selfless reduced group C*-algebras

18 Arie Levit: Invariant random subgroups of the finitary special linear group over a finite field

Fri, October 2

19 Fanny Kassel: Anosov representations and compact quotients

10:45 AM Coffee break

20 David Fisher: Dense subgroups of compact groups: two vignettes