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--- sessions:2023sessions:2023session1 [2023/03/24 09:28] – [Confirmed participants] ross.kang
+++ sessions:2023sessions:2023session1 [2023/09/13 08:09] (current) – [Talks (all times Central European Summer Time)] ross.kang
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   * Hidde Koerts
   * Aristotelis Chaniotis
+  * Paul Seymour
 * indicates speaker
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 Template: {{ sessions:2022sessions:opl-example.tgz| download}}
-Deadline: 21 March 2023
+Deadline: 21 March 2023 (closed)
 ==== Schedule (all times Central European Summer Time) ====
 We prioritise European participation, but to allow more possibilities for participation from different timezones as well as to keep the workshop lightweight, we limit most plenary activities to between 14:00 and 17:00.
-The following schedule is tentative:
 . //Monday, 27 March//
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   * 16:30 close of meeting
+==== Talks (all times Central European Summer Time) ====
+=== Sophie Spirkl: χ-boundedness and η-boundedness ===
+I will talk about η(G), the minimum size of a set of vertices X in G such that α(G\X) < α(G). This parameter has some surprising parallels with χ(G), and in particular, one can ask about “η-boundedness,” defined analogously to χ-boundedness. I will present some results and open questions about this.
+This is based on joint work with Sepehr Hajebi and Yanjia Li.
+:05, 28 March, https://uva-live.zoom.us/j/81672886664
+=== Alex Scott: On a problem of El-Zahar and Erdős ===
+Two subgraphs A, B of a graph G are anticomplete if they are vertex-disjoint and there are no edges joining them. Is it true that if G is a graph with bounded clique number, and sufficiently large chromatic number, then it has two anticomplete subgraphs, both with large chromatic number? This is a question raised by El-Zahar and Erdős in 1986, and remains open. If so, then at least there should be two anticomplete subgraphs both with large minimum degree, and that is one of our results.
+We prove two variants of this. First, a strengthening: we can ask for one of the two subgraphs to have large chromatic number. Second, we look at what happens if we replace the hypothesis that G has large chromatic number with the hypothesis that G has sufficiently large minimum degree. This, together with excluding K_t, is not enough to guarantee two anticomplete subgraphs both with large minimum degree; but it works if instead of excluding a complete graph we exclude a complete bipartite graph. Finally, we discuss analogous problems for tournaments.
+This is joint work with Tung Nguyen and Paul Seymour.
+:15, 29 March, https://us06web.zoom.us/j/88229832543?pwd=bmJidUVEcDJwaGZnTVJQNnFGTGdZQT09 (co-hosted by Jagiellonian TCS seminar)
+==== Research results ====
+  * Duraj, Kang, La, Narboni, Pokrývka, Rambaud, Reinald. The χ-binding function for d-directional segment graphs. https://arxiv.org/abs/2309.06072