[Binghamton Geometry Topology Seminar] Next week: Monday and Thursday talks!

[sapir at math.binghamton.edu]

Next week, we will meet twice: Monday at 4:30pm, and Thursday at 2:50 (as
usual).


SPECIAL DATE AND TIME: October 28, 4:30 - 5:30, WH 100E
 Speaker: Yash Lodha (EPFL)

 Title: Property FW and smoothability   Abstract: I shall describe joint
work with Matte Bon and  Triestino. We demonstrate that aperiodic actions
of Kazhdan groups by  countably singular diffeomorphisms on closed
manifolds are smoothable.  In the case of the circle, we obtain a proof
that groups of piecewise  linear or piecewise projective homeomorphisms
are not Kazhdan unless  they are finite. The key new idea is the
application of Property FW,  which is a weakening of Kazhdan's property (T).


October 31, 2:50 - 3:50pm, WH 100E
 Speaker: Eduard Schesler (Universitat Bielefeld)

 Title: The Sigma conjecture for solvable S-arithmetic groups via discrete
Morse theory on Euclidean buildings.


 Abstract: Given a finitely generated group G, the Σ invariants of G
consist of geometrically defined subsets Σk(G) of the set S(G) of all
characters χ:G→R of G. These invariants were introduced independently
by Bieri-Strebel and Neumann for k=1  and generalized by Bieri-Renz to the
general case in the late 80's in  order to determine the finiteness
properties of all subgroups H of G that contain the commutator subgroup
[G,G]. In this talk we determine the Sigma invariants of certain
S-arithmetic  subgroups of Borel groups in Chevalley groups. In
particular we will  determine the finiteness properties of every subgroup
of the group of  upper triangular matrices Bn(Z[1/p])<SLn(Z[1/p]) that
contains the group Un(Z[1/p]) of unipotent matrices where p is any
sufficiently large prime number.



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