Geometry/Topology Seminar
Fall 2017
Thursdays (and sometimes Tuesdays) 34pm, in
Eckhart 308

 Thursday September 28 at 34pm in Eck 308
 Andy Putman, Notre Dame
 The Johnson filtration is finitely generated

Abstract: A recent breakthrough of ErshovHe shows
that the Johnson kernel subgroup of the mapping class group
is finitely generated for g at least 12. In joint work with
Ershov and Church, I have extended this to show that every
term of the lower central series of the Torelli group is
finitely generated once the genus is sufficiently large. A
byproduct of our work is a proof that the Johnson kernel is
finitely generated for g at least 4 which is remarkably
simple (so simple, in fact, that I will be able to give in
nearly complete detail in this talk).

 Friday October 27
 Multiple speakers,
 (Conference) No Boundaries: Groups in Algebra, Geometry, and Topology
A Celebration of the Mathematical Contributions of Benson Farb

Abstract: Conference in honor of Benson Farb, 10/27
through 10/29. See
http://people.math.gatech.edu/~dmargalit7/noboundaries/schedule.shtml
for speakers.

 Thursday November 2 at 34pm in Eck 308
 Nate Harman, University of Chicago
 TBA

Abstract: TBA

 Thursday November 9 at 34pm in Eck 308
 Daniel Studenmund, Notre Dame
 Semiduality in group cohomology

Abstract: A duality group has a pairing exhibiting
isomorphisms between its homology and cohomology groups.
Examples include solvable BaumslagSolitar groups and
arithmetic groups over number fields, by work of Borel and
Serre. Many naturally occurring groups fail to be duality
groups, but are morally very close. In this talk we make
this precise with the notion of a semiduality group, and
prove that the lamplighter group is a semiduality group.
This illustrates methods used to prove the rank 1 case of a
general conjecture that certain arithmetic groups in
positive characteristic are semiduality groups, building on
the result of BorelSerre. This talk covers work joint with
Kevin Wortman.

 Thursday November 30 at 34pm in Eck 308
 Wouter Van Limbeek, Michigan
 TBA

Abstract: TBA

 Thursday December 7 at 34pm in Eck 308
 Phil Tosteson, Michigan
 TBA

Abstract: TBA

 Tuesday December 12 at 34pm in Eck 308
 Tathagata Basak, Iowa State
Due to the high number of requests, we are no longer accepting speakers via selfinvitations.
For questions, contact