L^2-Betti numbers of universal quantum groups

I will report on joint works with Julien Bichon, Sven Raum, Matthias Valvekens and Stefaan Vaes, revolving around the computation of L^2-Betti numbers for universal quantum groups. Among our main results is the fact that the first L^2-Betti number of the duals of the free unitary quantum groups equals 1, and that all other L^2-Betti numbers vanish. All objects mentioned in the abstract will be defined, more or less rigorously, during the talk.