Hyperlinear groups without the factorization property

Andreas Thom, 24 mars 2009, 11h15, CM1113

Title: Hyperlinear groups without the factorization property

Abstract: This talk is about various approximation properties a discrete group can have or fail to have. All notions will be motivated and explained in detail. We give an example of a group which is locally embeddable into finite groups (in particular it is initially subamenable, sofic and hence hyperlinear) but does not have Kirchberg's factorization property. This group provides also an example of a sofic Kazhdan group which is not residually finite, answering a question of Elek and Szabo. We also give an example of a group which is not initially subamenable but hyperlinear. Finally, we point out a mistake in an assertion of Kirchberg and provide an example of a group which does not have the factorization property and is still a subgroup of a connected finite-dimensional Lie group.