Title: Delocalized l2-Betti numbers and higher Kazhdan projections
Abstract: We explicitly describe higher Kazhdan projections for certain free product groups. Such description is obtained merely through the cohomological information in first degree about these groups. Employing this explicit description, as a byproduct we obtain new calculations of Lott's delocalized $\ell^2$-Betti numbers. In particular, we establish the first non-vanishing results for infinite groups. This is joint work with Sanaz Pooya.