buondì, vorrei annunciarvi il seminario di geometria di oggi, sempre alle 14 in aula seminari. (Mi scuso per il ritardo.) MERCOLEDI' 6 NOVEMBRE 2013 SEMINARI DI GEOMETRIA 14:00-15:00, Sala Seminari (Dip. Matematica) Bounded cohomology of graphs of groups Roberto Frigerio (Università di Pisa) Abstract: (joint work with M. Bucher, M. Burger, A. Iozzi, M.B. Pozzetti and C. Pagliantini) Abstract: Bounded cohomology of discrete groups or topological spaces are, usually, either trivial or quite wild. For example, while the bounded cohomology of Z vanishes in every positive degree, the 3rd and the 4th bounded cohomology of Z*Z is infinite dimensional (nothing is known about Z*Z in degree bigger than 3). In this seminar I will prove that the bounded cohomologies of the factors of an amalgamated product G isometrically embed into the bounded cohomology of G, provided that the amalgamation is along an amenable subgroup. As a corollary, I will describe a self-contained proof of the additivity of the simplicial volume with respect to gluings along amenable hypersurfaces.