Andrzej Zuk (Université Paris 7, and SPBSU)
Chebyshev Lab Special Lecture
Friday 20 April 17:00 room 14 (14-th line V.I., 29)
In 1924 Banach and Tarski proved that a ball in 3‑dimensional space can be decomposed into finitely many pieces which one could reassemble by rotations to form two copies of the original ball. We relate this to two fundamental notions in group theory: amenability (introduced by von Neumann) and property (T) (defined by Kazhdan).