[K-OS] Knot Online Seminar


[K-OS] is an online research seminar which focuses on knot theory and low-dimensional topology. It happens every Thursdays from 14:00 to 15:00 (CET/CEST Berlin, Brussels, Madrid, Paris, Rome, Vienna, Warsaw, Zurich) on Zoom.

It is organized by Louis-Hadrien Robert and Emmanuel Wagner. It benefits from logistical support from the CNRS and the university of Geneva.


13/05/2021
  • Speaker: William Ballinger (Princeton University)
  • Title: Concordance invariants from Khovanov homology.
  • Abstract: The Lee differential and Rasmussen's E(-1) differential acting on Khovanov homology combine to give a pair of cancelling differentials, an algebraic structure that has been studied in the context of knot Floer homology. I will describe some concordance invariants that come from this structure, with applications to nonorientable genus bounds and linear independence in the concordance group.


20/05/2021
  • Speaker: Delphine Moussard (Aix–Marseille Université)
  • Title: A triple point knot invariant and the slice and ribbon genera.
  • Abstract: The T-genus of a knot is the minimal number of borromean-type triple points on a normal singular disk with no clasp bounded by the knot; it is an upper bound for the slice genus. Kawauchi, Shibuya and Suzuki characterized the slice knots by the vanishing of their T-genus. I will explain how this generalizes to provide a 3-dimensional characterization of the slice genus. Further, I will show that the difference between the T-genus and the slice genus can be arbitrarily large. Finally, I will introduce the ribbon counterpart of the T-genus, which is an upper bound for the ribbon genus, and we will see that the T-genus and the ribbon T-genus coincide for all knots if and only if all slice knots are ribbon.


27/05/2021
  • Speaker: Agnès Gadbled (Université Paris–Saclay)
  • Title: TBA.
  • Abstract: TBA.


03/06/2021
  • Speaker: Yuta Nozaki (Hiroshima University)
  • Title: TBA.
  • Abstract: TBA.


10/06/2021
  • Speaker: Raphael Zentner (Universität Regensburg)
  • Title: TBA.
  • Abstract: TBA.


17/06/2021
  • Speaker: Vincent Colin (Université de Nantes)
  • Title: TBA.
  • Abstract: TBA.


24/06/2021

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