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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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TZID:Asia/Seoul
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TZOFFSETFROM:+0900
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DTSTART:20180101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20190910T163000
DTEND;TZID=Asia/Seoul:20190910T173000
DTSTAMP:20260422T225109
CREATED:20190903T042102Z
LAST-MODIFIED:20240707T090111Z
UID:1337-1568133000-1568136600@dimag.ibs.re.kr
SUMMARY:Kevin Hendrey\, The minimum connectivity forcing forest minors in large graphs
DESCRIPTION:Given a graph $G$\, we define $\textrm{ex}_c(G)$ to be the minimum value of $t$ for which there exists a constant $N(t\,G)$ such that every $t$-connected graph with at least $N(t\,G)$ vertices contains $G$ as a minor. The value of $\textrm{ex}_c(G)$ is known to be tied to the vertex cover number $\tau(G)$\, and in fact $\tau(G)\leq \textrm{ex}_c(G)\leq \frac{31}{2}(\tau(G)+1)$. We give the precise value of $\textrm{ex}_c(G)$ when $G$ is a forest. In particular we find that $\textrm{ex}_c(G)\leq \tau(G)+2$ in this setting\, which is tight for infinitely many forests.
URL:https://dimag.ibs.re.kr/event/2019-09-10/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20190919T163000
DTEND;TZID=Asia/Seoul:20190919T173000
DTSTAMP:20260422T225109
CREATED:20190815T090406Z
LAST-MODIFIED:20240707T090104Z
UID:1277-1568910600-1568914200@dimag.ibs.re.kr
SUMMARY:Cory Palmer\, A survey of Turán-type subgraph counting problems
DESCRIPTION:Let $F$ and $H$ be graphs. The subgraph counting function $\operatorname{ex}(n\,H\,F)$ is defined as the maximum possible number of subgraphs $H$ in an $n$-vertex $F$-free graph. This function is a direct generalization of the Turán function as $\operatorname{ex}(n\,F)=\operatorname{ex}(n\,K_2\,F)$. The systematic study of $\operatorname{ex}(n\,H\,F)$ was initiated by Alon and Shikhelman in 2016 who generalized several classical results in extremal graph theory to the subgraph counting setting. Prior to their paper\, a number of individual cases were investigated; a well-known example is the question to determine the maximum number of pentagons in a triangle-free graph. In this talk we will survey results on the function $\operatorname{ex}(n\,H\,F)$ including a number of recent papers. We will also discuss this function’s connection to hypergraph Turán problems.
URL:https://dimag.ibs.re.kr/event/2019-09-19/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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