Orateur(s)  Marek Kaluba  Karlsruhe Institute of Technology,

Titre  Introduction to property (T) and sums of squares 
Date  24/03/2022 
Horaire  10:00 à 11:00 

Diffusion  
Résume  We will start by looking into Cayley graphs of a group and build some geometric understanding of group Laplacians. Then we will look at their algebraic description in the group rings. This description allows to bridge Kazhdan property (T) and algebraic positivity of a certain operator in the group ring. We will explain how such positivity statements can be reformulated to a sum of squares decomposition problems. These in turn can be relaxed to problems of semidefinite optimization which can be effectively solved a computer. Finally I will say a few words on how such (imprecise) solution could be certified to form a mathematical proof of property (T).
The talk will be based on 1312.5431 by N.Ozawa and 1703.09680 by P.Nowak and myself. 
Salle  1013 
Adresse  Sophie Germain 