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X-WR-CALDESC:Events for Discrete Mathematics Group
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DTSTART;TZID=Asia/Seoul:20210203T163000
DTEND;TZID=Asia/Seoul:20210203T173000
DTSTAMP:20260422T201103
CREATED:20201106T054235Z
LAST-MODIFIED:20240705T193028Z
UID:3241-1612369800-1612373400@dimag.ibs.re.kr
SUMMARY:Ron Aharoni\, Colorful KKM and multiple cakes division
DESCRIPTION:In the “cake partition” problem n players have each a list of preferred parts for any partition of the [0\,1] interval (“cake”) into n sub-intervals. Woodall\, Stromquist and Gale proved independently that under mild conditions on the list of preferences (like continuity) there is always a partition and assignment of parts to the players\, in which every player gets a piece belonging to her list of preferred parts. In fact\, Gale proved a colorful version of the famous KKM theorem\, not realizing that this is the same problem\, but on the other hand\, proved the problem its proper setting. I will discuss the case of partitioning more than one cake – how many players can you make happy\, when there is a general number of cakes\, and general number of players. \nJoint work with Eli Berger\, Joseph Briggs\, Erel Segal-Halevi and Shira Zerbib.
URL:https://dimag.ibs.re.kr/event/2021-02-03/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20210210T163000
DTEND;TZID=Asia/Seoul:20210210T173000
DTSTAMP:20260422T201103
CREATED:20201231T073729Z
LAST-MODIFIED:20240705T191150Z
UID:3428-1612974600-1612978200@dimag.ibs.re.kr
SUMMARY:Jie Ma (马杰)\, Non-repeated cycle lengths and Sidon sequences
DESCRIPTION:We prove a conjecture of Boros\, Caro\, Furedi and Yuster on the maximum number of edges in a 2-connected graph without repeated cycle lengths\, which is a restricted version of a longstanding problem of Erdos. Our proof together with the matched lower bound construction of Boros\, Caro\, Furedi and Yuster show that this problem can be conceptually reduced to the seminal problem of finding the maximum Sidon sequences in number theory. Joint work with Tianchi Yang.
URL:https://dimag.ibs.re.kr/event/2021-02-10/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20210217T100000
DTEND;TZID=Asia/Seoul:20210217T110000
DTSTAMP:20260422T201103
CREATED:20201231T022333Z
LAST-MODIFIED:20240707T081843Z
UID:3423-1613556000-1613559600@dimag.ibs.re.kr
SUMMARY:David Wood\, Tree densities of sparse graph classes
DESCRIPTION:This talk considers the following question at the intersection of extremal and structural graph theory: What is the maximum number of copies of a fixed forest $T$ in an $n$-vertex graph in a graph class $\mathcal{G}$ as $n\to \infty$? I will answer this question for a variety of sparse graph classes $\mathcal{G}$. In particular\, we show that the answer is $\Theta(n^{\alpha_d(T)})$ where $\alpha_d(T)$ is the size of the largest stable set in the subforest of $T$ induced by the vertices of degree at most $d$\, for some integer $d$ that depends on $\mathcal{G}$. For example\, when $\mathcal{G}$ is the class of $k$-degenerate graphs then $d=k$; when $\mathcal{G}$ is the class of graphs containing no $K_{s\,t}$-minor ($t\geq s$) then $d=s-1$; and when $\mathcal{G}$ is the class of $k$-planar graphs then $d=2$. All these results are in fact consequences of a single lemma in terms of a finite set of excluded subgraphs. This is joint work with Tony Huynh (arXiv:2009.12989).
URL:https://dimag.ibs.re.kr/event/2021-02-17/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
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