BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Discrete Mathematics Group - ECPv6.15.20//NONSGML v1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-WR-CALNAME:Discrete Mathematics Group
X-ORIGINAL-URL:https://dimag.ibs.re.kr
X-WR-CALDESC:Events for Discrete Mathematics Group
REFRESH-INTERVAL;VALUE=DURATION:PT1H
X-Robots-Tag:noindex
X-PUBLISHED-TTL:PT1H
BEGIN:VTIMEZONE
TZID:Asia/Seoul
BEGIN:STANDARD
TZOFFSETFROM:+0900
TZOFFSETTO:+0900
TZNAME:KST
DTSTART:20200101T000000
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20210406T163000
DTEND;TZID=Asia/Seoul:20210406T173000
DTSTAMP:20260419T044432
CREATED:20210308T061306Z
LAST-MODIFIED:20240705T190041Z
UID:3731-1617726600-1617730200@dimag.ibs.re.kr
SUMMARY:Rutger Campbell\, Matroid orientability and representability
DESCRIPTION:In this talk we will have a brief introduction to oriented matroids and their relation to real-representability.
URL:https://dimag.ibs.re.kr/event/2021-04-06/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20210413T163000
DTEND;TZID=Asia/Seoul:20210413T173000
DTSTAMP:20260419T044432
CREATED:20210329T063026Z
LAST-MODIFIED:20240705T190013Z
UID:3866-1618331400-1618335000@dimag.ibs.re.kr
SUMMARY:William Overman\, Some Ordered Ramsey Numbers of Graphs on Four Vertices
DESCRIPTION:Ordered Ramsey numbers were introduced in 2014 by Conlon\, Fox\, Lee\, and Sudakov. Their results included upper bounds for general graphs and lower bounds showing separation from classical Ramsey numbers. We show the first nontrivial results for ordered Ramsey numbers of specific small graphs. In particular we prove upper bounds for orderings of graphs on four vertices\, and determine some numbers exactly using  SAT solvers for lower bounds. These results are in the spirit of exact calculations for classical Ramsey numbers and use only elementary combinatorial arguments. \nThis is joint work with Jeremy Alm\, Kayla Coffey\, and Carolyn Langhoff.
URL:https://dimag.ibs.re.kr/event/2021-04-13/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20210420T163000
DTEND;TZID=Asia/Seoul:20210420T173000
DTSTAMP:20260419T044432
CREATED:20210416T123209Z
LAST-MODIFIED:20240705T185049Z
UID:3946-1618936200-1618939800@dimag.ibs.re.kr
SUMMARY:Sang-il Oum (엄상일)\, What is an isotropic system?
DESCRIPTION:Bouchet introduced isotropic systems in 1983 unifying some combinatorial features of binary matroids and 4-regular graphs. The concept of isotropic system is a useful tool to study vertex-minors of graphs and yet it is not well  known. I will give an introduction to isotropic systems.
URL:https://dimag.ibs.re.kr/event/2021-04-20/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20210427T163000
DTEND;TZID=Asia/Seoul:20210427T173000
DTSTAMP:20260419T044432
CREATED:20210419T130854Z
LAST-MODIFIED:20240705T185048Z
UID:3961-1619541000-1619544600@dimag.ibs.re.kr
SUMMARY:Jungho Ahn (안정호)\, Well-partitioned chordal graphs with the obstruction set and applications
DESCRIPTION:We introduce a new subclass of chordal graphs that generalizes split graphs\, which we call well-partitioned chordal graphs. Split graphs are graphs that admit a partition of the vertex set into cliques that can be arranged in a star structure\, the leaves of which are of size one. Well-partitioned chordal graphs are a generalization of this concept in the following two ways. First\, the cliques in the partition can be arranged in a tree structure\, and second\, each clique is of arbitrary size. We mainly provide a characterization of well-partitioned chordal graphs by forbidden induced subgraphs and give a polynomial-time algorithm that given any graph\, either finds an obstruction or outputs a partition of its vertex set that asserts that the graph is well-partitioned chordal. We demonstrate the algorithmic use of this graph class by showing that two variants of the problem of finding pairwise disjoint paths between k given pairs of vertices are in FPT\, parameterized by k\, on well-partitioned chordal graphs\, while on chordal graphs\, these problems are only known to be in XP. From the other end\, we introduce some problems that are polynomial-time solvable on split graphs but become NP-complete on well-partitioned chordal graphs. \nThis is joint work with Lars Jaffke\, O-joung Kwon\, and Paloma T. Lima.
URL:https://dimag.ibs.re.kr/event/2021-04-27/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
END:VCALENDAR