Friday, 2019-06-07, 11:00-12:00, MPIM Seminar room
2019-07-03 and 2019-07-04
Wednesday, 03-07-2019, 14:00 -15:00, Danica
of the study group
Wednesday, 03-07-2019, 15:15 -16:15, Ben
Thursday, 04-07-2019, 15:15 -16:15, Danica
Thursday, 04-07-2019, 16:30 -17:30, Ben
November 2019
Monday, 04-11-2019, 15:00 - 16:00, Richard Porter
Abstract: In joint work with Alex Suciu, we explore finitely generated groups by studying the nilpotent towers and the various Lie algebras attached to such groups. The main goal is to relate an isomorphism extension problem in the Postnikov tower to the existence of certain commuting diagrams. This recasts a result of G. Rybnikov in a more general framework and leads to a generalization of Massey triple products and an application to hyperplane arrangements, whereby we show that all the nilpotent quotients of a decomposable hyperplane arrangement are combinatorially determined.
Tuesday, 05-11-2019, 14:00 - 15:00, Benjamin Ruppik
We'll start the second part of the study group by recalling the perspective on the Milnor invariants presented in July: They try to decide (inductively) how deep longitudes of link components lie in the lower central series of the link group.
Milnor's algebraic algorithm for calculating presentations of quotients G/G_{n} of the link groups is computationally very expensive, and because of this prior to Tim Cochran's work not many explicit examples were available. Cochran's perspective via iterated intersection of Seifert surfaces yields a machine that given any desired Milnor invariant can cook up a link which realizes this.
In this talk I'll explain how trees can be used to package all Milnor invariants of a given length in one piece, and how you can realize any given first non-vanishing Milnor invariant by iterated Bing-doubling.
Tuesday, 05-11-2019, 15:10 - 16:10, Mihail Arabadji
Tuesday, 05-11-2019, 16:30 - 17:30, Danica Kosanović
Thursday, 07-11-2019, 16:30 - 18:00, Peter Teichner
The study group is split into two parts:
Up-to-date information is in the 'Bonn low-dimensional topology' Google calendar; you can also check the MPIM calendar!