The GT seminar is intended to be an informal meeting place for students and researchers interested in topology in a broad sense. It is moderated by Roland van der Veen. There are no prerequisites, anyone interested can join. The seminar will meet on Mondays 2-3 at the Bernoulliborg (look at the schedule for the room of the day).

Date&room | Speaker | Topic | Notes |
---|---|---|---|

July 11, 2-3 room 289 | Wout Moltmaker (UvA) | New quantum invariants of planar knotoids | Reporting on joint work with Roland van der Veen, I will briefly introduce knotoids and discuss motivations for studying them, particularly showcasing applications to DNA and protein topology. Having motivated knotoids I will present a new invariant of (biframed) planar knotoids and show that it can distinguish planar knotoids that were previously not known to be distinct. Finally I will discuss virtual closures and talk about some aspects of the Kontsevich integral. |

June 20, 2-4 room 165 | Dror Bar-Natan (Toronto) | Cars, Interchanges, Traffic Counters, and a Pretty Darned Good Knot Invariant | Reporting on joint work with Roland van der Veen, I’ll tell you some stories about ρ1, an easy to define, strong, fast to compute, homomorphic, and well- connected knot invariant. ρ1 was first studied by Rozansky and Overbay, it has far-reaching generalizations, it is dominated by the coloured Jones polynomial, and I wish I un- derstood it. Handout available |

June 13, 2-3:30 room 289 | Fedel Berkenbosch, Lucas Taams and Reinder van der Weide | Three presentations on 3-manifolds and knots | There will be three 30 minute presentations each on a bachelor project in topology. |

May 30, room TBA | Jeffrey Weenink | The skein module of the three-torus | We will give an introduction to skein theory and compute the skein module of the 3-torus. |

May 23, room 165 | Roland van der Veen | 2D tessellations and 3d manifolds | We will give an overview of the geometry and topology of 3-manifolds with a focus on those that come from two-dimensional tilings. It turns out that the space of positions of any tessellation of plane, sphere or hyperbolic plane makes a very nice 3-manifold. Such manifolds are examples of the important class of Seifert manifolds that are in a natural way a disjoint union of circles. |

From February to May the GT seminar will coincide with the course Topics in Topology | See the course website | - | - |

Jan 31, room 2.22 online | Boudewijn Bosch | Seiberg-Witten theory | TBA |

Jan 24, room online | Jeffrey Weenink | Cluster algebras and triangulations | We introduce the cluster algebras and we relate it to the triangulation of surfaces. We see mutations as triangulation flips |

Jan 17, room online | Jorge Becerra | Cobordism and Thom spectra | I would like to sketch Thom's ideas to compute the (oriented) cobordism ring. What he showed is that computing the group of oriented n-manifolds modulo cobordism amounts to computing the n-th homotopy group of some "object". Notes |

Jan 10, room online | Roland van der Veen | Kick-off | |

Dec 6, room 5161.0289 or online | Kevin van Helden | Hyperplane arrangements | Kevin's slides |

Nov 29, room 5161.0293 | Boudewijn Bosch | Quantum representations of mapping class groups | Recording available |

Nov 22, room 5161.0293 | Surgery | Jeffrey Weenink | TBA |

Nov 16 NOTICE Tuesday!, room 5161.0105 | Jorge Becerra | Slice knots and Knot concordance | A slice knot is a knot that bounds a flat/smooth disk when pushed into 4-space. I will analyse and generalize this notion and give some basic examples. This talk serves as an introduction to one of the topics of the upcoming conference Winter braids XI. Handout for the talk available here. |

Nov 8, room 5161.0222 | Wout Moltmaker (UvA) | Reshetikhin-Turaev Knot(oid) Invariants | I will give a gentle introduction to the construction of Reshetikhin-Turaev invariants. This construction extracts an invariant of framed knots from every object of a fixed ribbon category. My exposition of Reshetikhin-Turaev invariants will be reasonably self-contained and requires little prerequisite knowledge. Time permitting, I will discuss knotoids and how to extend the construction of Reshetikhin-Turaev invariants to knotoids. Handout |

Nov 1, room 5173.0151 Linnaeusborg (start time 11:30) | Roland van der Veen | Knotted spheres in 4-space | Any knotted circle can be untied in four-space but what about a knotted sphere? I will show some examples of knotted spheres and how to present them using knotted graphs in ordinary space using Morse theory. As such an interesting challenge is to lift the techniques of knot theory first to knotted graphs and then to knotted spheres. |

Oct 25, room 5161.0222 | Martine Schut | Alexander polynomial and singular knots | I'll talk about deriving the crossing relations that can be used to find the Alexander polynomial from the fundamental group using the Wirtinger presentation. If time permits we can discuss extensions to singular crossing relations and/or the Dehn presentation. |

Oct 25, FMF meeting, room NB 5114.0004 | Roland van der Veen | Knots are portals to spaces unseen | Step through a door and you will enter a new room, but what if the doorway is knotted? Imagine a knot floating in front of you (I will bring a big one to the talk) and try to think of it as a door of some kind, a portal. Stepping through any of its loops will take you to a new room but how are the rooms interlinked? No previous knowledge of knots or topology is necessary to enjoy this talk. |

Oct 18, Academiegebouw | Thesis defense | Matthijs Ebbens | Delaunay triangulations of hyperbolic surfaces |

Oct 11, room Bernoulliborg 41b (ground floor) | Kick-off meeting. Hyperbolic geometry and Topology in dimension 3. | Roland van der Veen | On the occasion of the thesis defense of Matthijs next week I'd like to say a few words about the significance of hyperbolic geometry to topology. |

Dec 13-16 | Winter braids XI conference in Dijon | - | - |

- C. Adams, The Knot Book
- M. Armstrong, Basic Topology
- J. Munkres, Topology
- G. Francis, A topological picture book
- A. Hatcher, Algebraic topology
- D. Rolfsen, Knots and Links