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X-WR-CALNAME:Discrete Mathematics Group
X-ORIGINAL-URL:https://dimag.ibs.re.kr
X-WR-CALDESC:Events for Discrete Mathematics Group
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BEGIN:VTIMEZONE
TZID:Asia/Seoul
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TZOFFSETFROM:+0900
TZOFFSETTO:+0900
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DTSTART:20240101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20250513T163000
DTEND;TZID=Asia/Seoul:20250513T173000
DTSTAMP:20260417T000234
CREATED:20250218T070323Z
LAST-MODIFIED:20250310T022916Z
UID:10617-1747153800-1747157400@dimag.ibs.re.kr
SUMMARY:Seokbeom Kim (김석범)\, The structure of △(1\, 2\, 2)-free tournaments
DESCRIPTION:Given a tournament $S$\, a tournament is $S$-free if it has no subtournament isomorphic to $S$. Until now\, there have been only a small number of tournaments $S$ such that the complete structure of $S$-free tournaments is known. \nLet $\triangle(1\, 2\, 2)$ be a tournament obtained from the cyclic triangle by substituting two-vertex tournaments for two of its vertices. In this talk\, we present a structure theorem for $\triangle(1\, 2\, 2)$-free tournaments\, which was previously unknown. As an application\, we provide tight bounds for the chromatic number as well as the size of the largest transitive subtournament for such tournaments. \nThis talk is based on joint work with Taite LaGrange\, Mathieu Rundström\, Arpan Sadhukhan\, and Sophie Spirkl.
URL:https://dimag.ibs.re.kr/event/2025-05-13/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20250527T163000
DTEND;TZID=Asia/Seoul:20250527T173000
DTSTAMP:20260417T000234
CREATED:20250415T051555Z
LAST-MODIFIED:20250517T114823Z
UID:10778-1748363400-1748367000@dimag.ibs.re.kr
SUMMARY:Meike Hatzel\, Counterexample to Babai's lonely colour conjecture
DESCRIPTION:Motivated by colouring minimal Cayley graphs\, in 1978 Babai conjectured that no-lonely-colour graphs have bounded chromatic number. We disprove this in a strong sense by constructing graphs of arbitrarily large girth and chromatic number that have a proper edge colouring in which each cycle contains no colour exactly once. \nThe result presented is the joint work with James Davies and Liana Yepremyan.
URL:https://dimag.ibs.re.kr/event/2025-05-27/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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