[K-OS] Knot Online Seminar
[K-OS] is an online research seminar which focuses on knot
theory and low-dimensional topology. Talks will be delivered
by authors of recent arXiv articles of significant interest.
It happens the 3rd Thursday of every month
from 16:15 to 17:15
(
CET/CEST Berlin,
Brussels, Madrid, Paris, Rome, Vienna, Warsaw, Zurich)
on
Zoom.
It is organized by
Alexandra
Kjuchukova,
Lukas
Lewark,
Delphine
Moussard
and
Emmanuel
Wagner.
It benefits from logistical support from
the
CNRS, the university
of
Paris and the
ETHZ.
If there is a recent arXiv preprint which you would like to see featured on the seminar, please email the organizers with your suggestion.
The K-OS talks are also listed in a
Google Calendar.
Forthcoming Talks
19 February 2026
- Speaker: Yash Lodha (Purdue University)
- A solution to the Wiegold problem on perfect groups (arXiv:2510.26073)
- Abstract: A fundamental notion in group theory is the notion of the normal rank of a group. This is the smallest size of a set of elements, which if included in the set of relations, render the group trivial. The number of factors in the direct sum decomposition of the group abelianization provides a natural lower bound for the normal rank. The 1976 Wiegold problem on perfect groups asks whether there exist finitely generated perfect groups whose normal rank is greater than one. We demonstrate that free products of finitely generated perfect left orderable groups have normal rank greater than one. The solves the Wiegold problem, since there are a plethora of such examples. This is joint work with Lvzhou Chen.
26 March 2026
- Speaker: José Andrés Rodríguez Migueles (CIMAT)
- On the existence of universal links in three-manifolds (arXiv:2511.14985)
- Abstract: We will discuss the existence of branched coverings between closed 3-manifolds, with emphasis on universal knots and links. I will prove that the only closed 3-manifolds that admit a universal link are spherical. Furthermore, we distinguish between universal links and complement universal links and show that these notions do not coincide in general, by exhibiting infinitely many examples of complement universal links that are not universal. Also, we prove that there is no closed aspherical 3-manifold, such that every closed, aspherical 3-manifold is a branched covering over it. Finally, we characterize the closed 3-manifolds admitting branching coverings from P3#P3, and deduce that there is no closed reducible 3-manifold, such that every closed reducible 3-manifold is a branched covering over it. This a work in colaboration with Araceli Guzmán, Jesús Rodríguez and Francisco González-Acuña.
