[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
30/09/2021
7/10/2021
14/10/2021
21/10/2021
28/10/2021
28/10/2021
4/11/2021NO SEMINAR
11/11/2021
18/11/2021
25/11/2021NO SEMINAR
2/12/2021
9/12/2021
16/12/2021
