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X-WR-CALDESC:Events for Discrete Mathematics Group
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DTSTART:20220101T000000
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DTSTART;TZID=Asia/Seoul:20230215T163000
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SUMMARY:Robert Hickingbotham\, Treewidth\, Circle Graphs and Circular Drawings
DESCRIPTION:A circle graph is an intersection graph of a set of chords of a circle. In this talk\, I will describe the unavoidable induced subgraphs of circle graphs with large treewidth. This includes examples that are far from the `usual suspects’. Our results imply that treewidth and Hadwiger number are linearly tied on the class of circle graphs\, and that the unavoidable induced subgraphs of a vertex-minor-closed class with large treewidth are the usual suspects if and only if the class has bounded rank-width. I will also discuss applications of our results to the treewidth of graphs $G$ that have a circular drawing whose crossing graph is well-behaved in some way. In this setting\, our results show that if the crossing graph is $K_t$-minor-free\, then $G$ has treewidth at most $12t-23$ and has no $K_{2\,4t}$-topological minor. On the other hand\, I’ll present a construction of graphs with arbitrarily large Hadwiger number that have circular drawings whose crossing graphs are $2$-degenerate. This is joint work with Freddie Illingworth\, Bojan Mohar\, and David R. Wood
URL:https://dimag.ibs.re.kr/event/2023-02-15/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
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