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 → 10:00 AM Welcome Coffee/ Badge Distribution

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

10:10 AM → 10:55 AM Uri Bader: How to get infected with Lp-cohomology and how to cure it?

10:55 AM → 11:15 AM Coffee break

11:15 AM → 12:00 PM Simon Machado: Quantitative growth of the injectivity radius

12:00 PM → 2:00 PM Lunch

2:00 PM → 2:45 PM Adrian Ioana: Rigidity for graph product von Neumann algebras

2:45 PM → 3:15 PM Coffee break

3:15 PM → 4:00 PM Ursula Hamenstädt: Mixing and counting in relatively hyperbolic groups

4:15 PM → 5:00 PM Hanna Oppelmayer: Random subalgebras

Tue, September 29

10:00 AM → 10:45 AM Emmanuel Breuillard: Expander Cayley graphs and non-abelian Littlewood-Offord

10:45 AM → 11:15 AM Coffee break

11:15 AM → 12:00 PM Tianyi Zheng: Commensurating actions and the Sierpiński carpet group

12:00 PM → 12:10 PM Group Photo

12:10 PM → 2:00 PM Lunch

2:00 PM → 2:45 PM Yehuda Shalom: Progress on the Margulis-Zimmer conjecture

2:45 PM → 3:15 PM Coffee break

3:15 PM → 4:00 PM Goulnara Arzhantseva: Simple and selfless reduced group C*-algebras

4:15 PM → 5:00 PM Corentin Le Bars: Charmenability of twin building lattices

6:00 PM → 8:30 PM Cocktail

Wed, September 30

9:30 AM → 10:15 AM Pierre-Emmanuel Caprace: Mixing versus amenability for unitary representations of groups acting on buildings

10:15 AM → 10:45 AM Coffee break

10:45 AM → 11:30 AM Denis Osin: A paradoxical route from hyperbolic geometry to proper proximality

11:30 AM → 12:15 PM Shirly Geffen: Stable rank one in nonnuclear C*-algebras

Thu, October 1

10:00 AM → 10:45 AM Waltraud Lederle: Boomerang subgroups, Schreier graphs and avoiding invariant measures

10:45 AM → 11:15 AM Coffee break

11:15 AM → 12:00 PM Mehrdad Kalantar: On Invariant Random Subgroups of C*-Simple Groups

12:00 PM → 2:00 PM Lunch

2:00 PM → 2:45 PM Sven Raum: K-theory and delocalised traces of right-angled Hecke C*-algebras

2:45 PM → 3:15 PM Coffee break

3:15 PM → 4:00 PM Itamar Vigdorovich: Selfless reduced group C*-algebras

4:15 PM → 5:00 PM Arie Levit: Invariant random subgroups of the finitary special linear group over a finite field

Fri, October 2

10:00 AM → 10:45 AM Fanny Kassel: Anosov representations and compact quotients

10:45 AM → 11:15 AM Coffee break

11:15 AM → 12:00 PM David Fisher: Dense subgroups of compact groups: two vignettes