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.