[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 Alexandra Kjuchukova, Lukas Lewark, Louis-Hadrien Robert and Emmanuel Wagner. It benefits from logistical support from the CNRS and the university of Geneva.

We are coming back after a summer break. Happy holidays and see you in September!



Forthcoming Talks


9/09/2021

16/09/2021
  • Speaker: Dan Cristofaro-Gardiner (University of Maryland)
  • Title: The Simplicity Conjecture
  • Abstract: In the 60s and 70s, there was a flurry of activity concerning the question of whether or not various subgroups of homeomorphism groups of manifolds are simple, with beautiful contributions by Fathi, Kirby, Mather, Thurston, and many others. A funnily stubborn case that remained open was the case of area-preserving homeomorphisms of surfaces. For example, for balls of dimension at least 3, the relevant group was shown to be simple by work of Fathi from the 1970s, but the answer in the two-dimensional case was not known. I will explain recent joint work proving that the group of compactly supported area preserving homeomorphisms of the two-disc is in fact not a simple group, which answers the "Simplicity Conjecture" in the affirmative. Our proof uses a new tool for studying area-preserving surface homeomorphisms, called periodic Floer homology (PFH) spectral invariants; these recover the classical Calabi invariant of monotone twists. I will also briefly mention a generalization of our result to compact surfaces of any genus.


23/09/2021
  • Speaker: TBA
  • Title: TBA


30/09/2021
  • Speaker: TBA
  • Title: TBA


7/10/2021

14/10/2021
  • Speaker: TBA
  • Title: TBA


21/10/2021
  • Speaker: TBA
  • Title: TBA


28/10/2021
  • Speaker: TBA
  • Title: TBA


28/10/2021

4/11/2021
NO SEMINAR


11/11/2021

18/11/2021

25/11/2021
NO SEMINAR


2/12/2021
  • Speaker: TBA
  • Title: TBA


9/12/2021
  • Speaker: TBA
  • Title: TBA


16/12/2021
  • Speaker: TBA
  • Title: TBA

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