Prof. S. Friedl PhD / Prof. Dr. C. Lh

In this seminar we will cover various topics in topology and geometric group theory.


In WS 23/24: We will meet on Friday, 10:15--11:45 (M201). Please register in GRIPS if you are interested in participating in this seminar.

Scheduled meetings/talks in SS 24

Date Topic Speaker
April 26 "The" cube category Georg Thurner
May 3 Tanushree Shah (Vienna)
May 10 Wachstumsreihen von Gruppen [in German] Johannes Weiß
May 17 The homeomorphism problem for 4-manifolds Matthias Uschold
May 31 Twisted Alexander polynomials of hyperbolic knots Stefan Friedl
June 7 Primality tests and factorisation methods Sabine Kiefl
June 14 Outside the topology box: Orbit equivalence Clara Löh
June 21 Profinite rigidity and amenability Anna Cascioli
June 28 Large homology spheres Matthias Holzammer
July 5 The hyperboloid model and reflection groups Benjamin Takacs
July 12 G-Theory of group rings Malena Wasmeier
July 19 Persistent cohomology and cup products Daniel Zach

Scheduled meetings/talks in WS 23/24

Date Topic Speaker
October 20 Das Alexanderpolynom von Satellitenknoten Tobias Hirsch
October 27 The Kirby Torus Trick for Surfaces Max Schopf
November 3 ... Fortsetzung Max Schopf
November 10 Growth rates in hyperbolic groups Hannes Lohberger (online)
(zoom access data: see GRIPS page; M 201 will be open, but you will need to bring your own device)
November 17 Persistent homology analysis of the evolution of SARS-CoV-2 Alison Durst
November 24 Borsuk--Ulam Theorem Konstantin Priller
December 1 Der Vierfarbensatz (in German) Jan Käsbauer
December 8 Tubular neighbourhoods Stefan Friedl
December 15 Conformal Dimension of the Boundary for Hyperbolic Coxeter Groups Julia Heller (KIT)
January 12 Bring your favourite conjecture! everybody
January 19 Bring your favourite conjecture!, Part II everybody
January 26 arXivoloy: bring your favourite arXiv preprint from 2023 or 2024! everybody
February 2 arXivoloy: bring your favourite arXiv preprint from 2023 or 2024! Part II everybody
February 9 De Rham cohomology Weichen Xue

Scheduled meetings/talks in SS 23

Date Topic Speaker
April 21 Implementing Pachner's Theorem with Lean Garett Cunningham
April 28 Gauss linking number Stefan Friedl
May 5 Singularities, fibered knots and cobordisms Filip Misev
May 12 Minimal volume with different tools Ulrich Steindl
May 19 A Monster's Expedition (through Puzzling Exhibitions); eine mathematische Analyse Sebastian Freiberger
May 26 The Fekete Lemma and more Clara Löh
June 2 H-Raum-Struktur auf Sphären und K-Theorie Patrick Perras
June 9 Selberg's lemma Eider Gonzalo
June 16 Bounded cohomology, quasi-morphisms, and cup-products Franziska Hofmann
June 23, H 7 (!!) tba talk cancelled Julia Heller (KIT)
June 30 Spectra of manifolds and random walks Tim Höpfner (Göttingen)
July 7 Asymptotic cones of bi-invariant metrics on groups Jarek Kedra (University of Aberdeen)
July 14 Geometric von Neumann problems on non-amenability Simon Stahl
July 14 note: at 13:15 there is another talk in M311 that is LKS-related! Jayden Hammet (University of Melbourne)
July 21 Der Satz von Peter und Weyl Lisa Schambeck
July 25, 12:15, M 104 tba José Pedro Quintanilha

Scheduled meetings/talks in WS 22/23

Date Topic Speaker
October 21 arXivology (bring your favourite arXiv preprint from 2022) everybody
October 28 Blanchfield pairings and Gordian distance Stefan Friedl
November 4 arXivology, continued (from Oct 21) everybody
November 11 Laws and freedom (of groups) Clara Löh
November 18 Simplicial volume of closed locally homogeneous Riemannian manifolds [zoom talk] Peng Hui How (UChicago)
November 25 Khovanov Homology and the \lambda-Invariant Damian Iltgen
December 2 Sigma-Invariants José Pedro Quintanilha (U Bielefeld)
December 9 How to make Heegaard diagrams nice Ludovico Morellato
December 16 Homology growth and cheap rebuilding of inner-amenable groups Matthias Uschold
December 22(!), 14:15, M 201 Meridional rank of Whitehead doubles Ederson Dutra
January 13 Pseudo-Anosov maps Filip Misev
January 20 Homology theories in cofibration categories Divya Ghanshani
January 27 Homology spheres Elisabeth Kraus
February 3 Multicurves of double tangles Claudius Zibrowius
February 10 A QI-invariant cop number Margarete Diem

Scheduled meetings/talks in SS 22

Date Topic Speaker
April 29 Projects/Reading/Plans: Show-and-tell everybody
May 6 Regular homotopy of curves Stefan Friedl
May 13 Surjunctive groups Thomas Hilz
May 20 The monodromy group of a positive braid Livio Ferretti (Bern)
May 27 Goodwillie calculus and \infty-categories Johannes Witzig
June 3 Excisive Approximation of l^1-Homology Johannes Witzig
June 10 Integral foliated simplicial volume and ergodic decomposition Giovanni Sartori
June 17 Concordance and alternation numbers of positive 3-braid knots (and a knot homology invariant) Paula Truöl (ETHZ)
June 24 A tale of two algebraic notions: left orderability and local indicability (abstract) Yash Lodha (Universität Wien)
July 1 Gauge-theoretic invariants of three-manifolds with a torus boundary component, and contact geometry Tom Hockenhull (MPIM Bonn)
July 8 Graph braid groups and Topological Complexity (M 311) Giada Serafini (HHU Düsseldorf)
July 15 L^2-invariants and Representation theory (M 311) Han Zhicheng (G-A-U Göttingen)
July 22 Thurston Spine of Teichmueller space Ingrid Irmer
July 29 Representations of fundamental groups via instantons Felix Eberhart

Scheduled meetings/talks in WS 21/22

Date Topic Speaker
October 19, 10:15, M 103 (hybrid on demand) Computability and L2-Betti numbers Matthias Uschold
October 26, 10:15, M 201 (?) Pachner's theorem, II Julian Hannes
November 2, 10:15, M 201 (?) Computability and L2-Betti numbers II (moved to Nov 16; instead we talked on Sigma invs and OEIS) Matthias Uschold
November 9, 10:15, M 201 (?) Spectral sequences in bounded cohomology Daniel Echtler
November 16, 10:15, M 311 (hybrid on demand) Computability and L2-Betti numbers II Matthias Uschold
November 23, 10:15, M 311 (hybrid on demand) Seifert genus and multicurves Benedikt Aubeck
November 30, 10:15, M 311 (hybrid) Bits and pieces (possibly also triple points!) everybody
December 7, 10:15, M 311 (hybrid) aspherical manifolds and simply(cial) thanks vous(lume) Marco Moraschini
December 14, 10:15, online Smooth structures on non-compact 4-manifolds Isacco Nonino (U Bonn)
December 21, 10:15, online Enlargeability and Relativitiy Jonathan Glöckle
January 11, 10:15, M 311 (hybrid on demand) The Thom-Pontryagin construction Stefan Friedl
January 18, 10:15, M 311 (hybrid on demand) The Arf invariant and pi_{n+2}(S^n) Stefan Friedl
January 25, 10:15, M 311 (hybrid on demand) Realizing groups via graphs of groups with restricted vertices Alessandro De Innocentiis
February 1, 10:15 From genera to number theory Wenbo Liao
February 8, 10:15, probably online tba Kevin Li (University of Southampton)
February 25, 8:15, online TDA Linda Hu

Scheduled meetings/talks between SS 2021 and WS 21/22

Date Topic Speaker
September 17, 11:00, H 31 The universal covering from a categorial point of view Benedikt Löhlein
October 8, time: 11:00, location: H 31 (hybrid) The Novikov additivity theorem Stefan Friedl
October 15, 11:00, M 101 (hybrid) Strong Haken via Sphere Complexes Sebastian Hensel (LMU)

Scheduled meetings/talks in SS 2021 (online)

Date Topic Speaker
April 13 The (generalised) Toeplitz problem Ulrich Steindl
April 20 no talk
April 27 Bring your favourite group! everybody
May 4 LS-cat and applications Marco Moraschini
May 11 no talk (SFB prep) SFB subset
May 18 How to see a singularity Filip Misev
May 25 no talk! (Whit Tuesday)
May 26 (Wed!!) Complexity of Seifert manifolds Valentina Falcioni (Bologna)
10:15--11:45 if there is no Oberseminar; otherwise, we will move to 8:30--10:00.
June 1 no talk! (SFB eval)
June 8 Bring your favourite group! II everybody
June 15 Categorical invariants of groups via classifying spaces for families Kevin Li (University of Southampton)
June 22 L^p-geometry of diffeomorphism groups: old and new results Michael Brandenbursky (virtual Humboldt guest)
June 29 Trees and mapping class groups José Pedro Quintanilha
July 6 CAT(0)-Geometry Simon Stahl
July 13 Cancellation of handles Jan Zwank

Scheduled meetings/talks in 02--04 2021 (online)

Date Topic Speaker
February 25 Octonionic projective space Stefan Friedl
March 4 Spatial graphs José Pedro Quintanilha/Lars Munser
March 11 A pedestrian's view of Fukaya categories of surfaces Claudius Zibrowius
March 18 Sagemath interface to knotinfo Sebastian Oehms
March 25 Sperner's Lemma Lukas Lewark
April 1 Pachner's theorem Julian Hannes

Scheduled meetings/talks in WS 2020/21 (online)

Date Topic Speaker
October 2 (Fri!) Conway mutation in link Floer, Khovanov and Bar-Natan homology Claudius Zibrowius
October 8 (Thu!) Projective modules and the homotopy classification of CW-complexes Johnny Nicolson (UCL)
October 12 (Mon! 10:15) Conway mutation in link Floer, Khovanov and Bar-Natan homology; part II Claudius Zibrowius
October 15 (Thu!) A lower bound on the stable 4-genus of knots Damian Iltgen
October 22 (Thu!) Stallings Theorem and link concordance Lars Munser
October 29 (Thu!) Mapping classes are almost determined by their finite quotient actions José Pedro Quintanilha
November 3 Real-world amenable coverage problems and bounded cohomology Pietro Capovilla
November 10 Integral foliated simplicial volume of mapping tori Mathias Steinhuber
November 17 Khovanov homology and the unknotting number Laura Marino
November 24 What are the Betti numbers of closed manifolds? Matthias Kreck (Bonn)
December 1 Introduction to the Isabelle proof assistant Peter Bonart
December 8 On the Berstein-Svarc theorem in dimension 2 Habib Alizadeh
December 15 Mapping class groups of aspherical manifolds Christoph Winges
January 12 arXivology everybody
January 19 An introduction to TQFTs George Raptis
January 26 Convergence of twisted Alexander polynomials Georg Lipp

Scheduled meetings/talks in SS 2020 (online)

Date Topic Speaker
May 7 Simplicial volume via normalised cycles Marco Moraschini
May 14 Milnor-Wood ohne Kontaktverbot (but in English) Jonathan Bowden
May 21 -- Holiday
May 28 Berkovich spaces Miriam Prechtel
June 4 Higher multiplicities of the Dirac operator Julian Seipel
June 11 -- Holiday
June 18 Topology without topology Stefan Friedl
June 25 Normed p-adic amenability Francesco Fournier Facio (ETH Zürich)
July 2 Products Stefan Friedl
July 9 More products More Friedl
July 16 Twisted Kuperberg invariants and Reidemeister torsion Daniel López-Neumann
July 23 The Hopf conjecture on mapping degrees Michael Friesen

Scheduled meetings/talks in WS 2019/20

Date Topic Speaker
October 18 Let X be a scheme ... Johannes Witzig
October 25 Classifying spaces and orbit categories Daniel Echtler
November 1 holiday
November 8 Descriptive set theory and forcing Kristin Geßler
November 15 The l^1-semi-norm on singular homology in degree 2 Stephanie Ortmann
November 22 Split-braid-merge diagrams, 3-manifolds, and conjugacy in a braided Thompson group Yuri Santos Rego (OvGU Magdeburg)
November 29 Higer order intersection numbers in 4-manifolds Lars Munser
December 6 no talk (Bavarian Geometry and Topology Meeting, Augsburg) --
December 13 More intersection numbers Lars Munser
December 20
January 10 The uniform boundary condition on free groups Simon Lang
January 17 The Cimasoni-Florens signatures of links Andreas Wicher
January 24 The maximum volume of hyperbolic polyhedra (in M311!) Giulio Belletti (Scuola Normale Superiore, Pisa)
January 31 Homological algebra for l^1-homology Florian Greindl
February 7 Chromatische Zahl von Kneser-Graphen und Borsuk-Ulam-Satz Tobias Frey
February 26 (Wed, 10:15) Daniel Grünbaum

Scheduled meetings/talks in SS 2019

Date Topic Speaker
April 26 Prime decomposition of high-dimensional manifolds Stefan Friedl
May 3 Discrete Morse theory Michał Marcinkowski (Wrocław)
May 10 no talk, but there is an extra talk on May 16 (see below)
May 16 14:30--15:30, M104; Whitney towers and higher order intersection numbers Lars Munser (Bonn)
May 17 Excision (from a different viewpoint) Johannes Witzig
May 23 15:00--16:00, M104; Homology operations of little 2-cubes algebras Domenico Marasco (Bonn)
May 24 Introduction to sl_3 homology of knots Carlo Collari ()
May 31 The Reidemeister-Schreier algorithm Muriel Garcia
June 7 Twist knots and Casson-Gordon invariants Damian Iltgen
June 14 Stable classification of 4-manifolds Benjamin Ruppik (Bonn)
June 21 The table theorem José Pedro Quintanilha
June 28 Excision: The wishlist Johannes Witzig
July 5 Chromatic number of groups (8:25--9:55!) Matthias Uschold
July 12 Hashing via expander graphs Yannick Lautner
July 19 The Svarc-Milnor Lemma Pia Knerich
July 26 On the isomorphism problem for (hyperbolic) one-relator groups Alan Logan (Heriot-Watt University)
August 2 The rendez-vous value of topological spaces Jan-Philipp Zwank

Scheduled meetings/talks in WS 2018/19

Date Topic Speaker
October 19 (M311!) Lower bounds on Dehn functions of residually free groups Claudio LLosa-Isenrich (PSUD)
October 26 Minimal stretch factors in the extended mapping class groups Livio Liechti (IMJ)
November 2 no talk --
November 9 Hilbert spaces over non-archimedean fields Raphael Schmidpeter
November 16 (10:00 s.t.!) Hopf algebras in Galois theory Linda Hu
November 23 Vassiliev invariants via manifold calculus Yuqing Shi (Bonn)
November 30 Lagrangian relations, cobordisms and the Maslov index Enrico Toffoli
December 7 part 2 Enrico Toffoli
December 14 Geometry/Topology meeting in Augsburg
December 21 Bieri-Neumann-Strebel Transchromatic Theory with Quasi Theory Gerrit Herrmann
January 11 Scanning maps (?) Luigi Caputi
January 18 Some faces of the Poincaré homology 3-sphere José Pedro Quintanilha
January 25 Simplicial Poincaré Duality Bruno Mazorra
(additional talk of the seminar Topology vs. Combinatorics)
February 1 tba Alexandra Kjuchukova (MPIM)
February 8 moved to Wed, Feb 6, 14:00 Kai Zehmisch (Gießen)

Scheduled meetings/talks in SS 2018

Date Topic Speaker
April 12 Fibred classes Stefan Friedl
April 19 Homological stability for Artin monoids Rachael Boyd (University of Aberdeen)
April 26 Irrfahrten, Satz von Polya Leonhard Beutlhauser
May 3 Irrfahrten auf 3-Mannigfaltigkeiten Richard Mante
May 10 -- Ascension Day
May 17 Exceptional manifolds Stefan Friedl
May 24 Surgery theory for dummies/beginners Markus Land
May 31 -- Corpus Christi
June 7 Klassifikation von Seifert-gefaserten 3-Mannigfaltigkeiten Felix Eberhart
June 14 10 Reasons why profinite groups are important in the world around you José Pedro Quintanilha
June 21 Der Satz von Helly Julian Hannes
June 28 Configuration spaces of linkages Dennis Zumbil
July 5 A Tale of Three Embeddings of Group Rings Fabian Henneke (Bonn)
July 12 An introduction to machine learning Jonas Kleinöder
July 19 Simplicial volume of surfaces with finite coefficients Michael Friesen


entry in the commented list of all courses.

Last change: 01/2024