[Binghamton Geometry/Topology Seminar] 2 talks October 22

[Marco Varisco]

Binghamton Geometry/Topology Seminar
http://www.math.binghamton.edu/dept/topsem/

Two talks are scheduled for this Thursday.


-- First talk --

Date: Thursday, October 22, 2009

Time: 2:50-3:50 pm

Place: Library North 2205
(followed by coffee/tea in the Anderson Reading Room)

Speaker: Mark V. Sapir, Vanderbilt University

Title: Residual properties of 1-related groups

Abstract: This is a joint work with A. Borisov and I. Spakulova. We
prove that almost all 1-related groups with at least 3 generators are
residually finite and coherent. The proof uses geometric group theory,
algebraic geometry, and probability theory (Wiener's measure).


-- Second talk --

Date: Thursday, October 22, 2009

Time: 4:30-5:30 pm
(preceded by coffee/tea in the Anderson Reading Room)

Place: Library North 2205

Speaker: Jonathan Hillman (University of Sydney)

Title: Indecomposable PD3-complexes

Abstract: If X is a PD3-complex which is indecomposable as a connected
sum then either it is aspherical or its fundamental group is virtually
free, and hence is the fundamental group of a reduced finite graph of
finite groups, by work of Turaev and Crisp. We show that if X is an
indecomposable PD3-complex and π1(X) = πG, where G is such a graph of
groups, then either Z nor Z+Z/2Z or X is orientable, the underlying
graph is a tree, the vertex groups have cohomological period dividing
4 and all but at most one of the edge groups is Z/2Z. If there are no
exceptions then all but at most one of the vertex groups is dihedral
of order 2m with m odd. Every such group is realized by some
PD3-complex. Otherwise, one edge group may be Z/6Z. We do not know of
any such examples.