[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

21 May 2026

• Speaker: Simeon Hellsten (University of Glasgow)
• Cobordism and Concordance of Surfaces in 4-Manifolds (arXiv:2601.22152)
• Abstract: In this talk, we will complete the classification of compact surfaces in oriented 4-manifolds up to (unoriented) cobordism, and of compact surfaces in simply-connected 4-manifolds up to concordance. Instead of the homotopy-theoretic techniques pioneered by Thom that suffice for oriented cobordism, we approach the unoriented cobordism classification using novel geometric and combinatorial techniques. The concordance classification adapts the ambient surgery strategy of Kervaire and Sunukjian to the unoriented setting by using Pin^- structures.