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PRODID:-//Discrete Mathematics Group - ECPv5.0.1//NONSGML v1.0//EN
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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
BEGIN:VTIMEZONE
TZID:Asia/Seoul
BEGIN:STANDARD
TZOFFSETFROM:+0900
TZOFFSETTO:+0900
TZNAME:KST
DTSTART:20200101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200225T163000
DTEND;TZID=Asia/Seoul:20200225T173000
DTSTAMP:20200219T031121
CREATED:20200217T133320Z
LAST-MODIFIED:20200218T105011Z
UID:2129-1582648200-1582651800@dimag.ibs.re.kr
SUMMARY:Xin Zhang (张欣)\, On the equitable tree-coloring of graphs with low degeneracy
DESCRIPTION:A (vertex) $k$-coloring of a graph $G$ is a tree-coloring if each color class induces a forest\, and is equitable if the sizes of any two color classes differ by at most 1. The first relative result concerning the equitable tree-coloring of graphs is due to H. Fan\, H. A. Kierstead\, G. Liu\, T. Molla\, J.-L. Wu\, and X. Zhang (2011)\, who proved that any graph with maximum degree at most $\Delta$ has a $\Delta$-coloring so that each color class induces a graph with maximum degree at most 1. After that\, many results on this topic were published in the literature. For example\, L. Esperet\, L. Lemoine\, and F. Maffray (2015) showed that any planar graph admits an equitable tree-$k$-coloring for every integer $k\ge 4$，and G. Chen\, Y. Gao\, S. Shan\, G. Wang\, and J.-L. Wu (2017) proved that any 5-degenerate graph with maximum degree at most $\Delta$ admits an equitable tree-$k$-coloring for every $k\geq \lceil\frac{\Delta+1}{2}\rceil$. \nIn this talk\, we review part of the known results and the conjectures on the equitable tree-coloring of graphs\, and then show the sketch proofs of our three new results as follows: \n(a) the vertex set of any graph $G$ can be equitably partitioned into $k$ subsets for any integer $k\geq\max\{\lceil\frac{\Delta(G)+1}{2}\rceil\,\lceil\frac{|G|}{4}\rceil\}$ so that each of them induces a linear forest; \n(b) any plane graph with independent crossings admits an equitable tree-$k$-coloring for every integer $k\ge 8$; \n(c) any $d$-degenerate graph with maximum degree at most $\Delta$ admits an equitable tree-$k$-coloring for every integer $k\geq (\Delta+1)/2$ provided that $\Delta\geq 10d$. \nThis is a joint work with Yuping Gao\, Bi Li\, Yan Li\, and Bei Niu. \n
URL:https://dimag.ibs.re.kr/event/2020-02-25/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200303T163000
DTEND;TZID=Asia/Seoul:20200303T173000
DTSTAMP:20200219T031121
CREATED:20200207T093644Z
LAST-MODIFIED:20200207T093644Z
UID:2099-1583253000-1583256600@dimag.ibs.re.kr
SUMMARY:Eun-Kyung Cho (조은경)\, Decomposition of a planar graph into a $d$-degenerate graph and a graph with maximum degree at most $h$
DESCRIPTION:Given a graph $G$\, a decomposition of $G$ is a collection of spanning subgraphs $H_1\, \ldots\, H_t$ of $G$ such that each edge of $G$ is an edge of $H_i$ for exactly one $i \in \{1\, \ldots\, t\}$. Given a positive integer $d$\, a graph is said to be $d$-degenerate if every subgraph of it has a vertex of degree at most $d$. Given a non-negative integer $h$\, we say that a graph $G$ is $(d\,h)$-decomposable if there is a decomposition of $G$ into two spanning subgraphs\, where one is a $d$-degenerate graph\, and the other is a graph with maximum degree at most $h$. \nIt is known that a planar graph is $5$-degenerate\, but not always $4$-degenerate. This implies that a planar graph is $(5\,0)$-decomposable\, but not always $(4\,0)$-decomposable. Moreover\, by related previous results\, it is known that a planar graph is $(3\,4)$- and $(2\,8)$-decomposable. \nIn this talk\, we improve these results by showing that every planar graph is $(4\,1)$-\, $(3\,2)$-\, and $(2\,6)$-decomposable. The $(4\,1)$- and $(3\,2)$-decomposabilities are sharp in the sense that the maximum degree condition cannot be reduced more. \nThis is joint work with Ilkyoo Choi\, Ringi Kim\, Boram Park\, Tingting Shan\, and Xuding Zhu. \n
URL:https://dimag.ibs.re.kr/event/2020-03-03/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200512T163000
DTEND;TZID=Asia/Seoul:20200512T173000
DTSTAMP:20200219T031121
CREATED:20200211T143841Z
LAST-MODIFIED:20200211T143841Z
UID:2116-1589301000-1589304600@dimag.ibs.re.kr
SUMMARY:Iain Moffatt\, From graph duals to matrix pivots: a tour through delta-matorids
DESCRIPTION:This talk will consider a variety of everyday graph theoretical notions — duals\, circle graphs\, pivot-minors\, Eulerian graphs\, and bipartite graphs — and will survey how they appear in the theory of delta-matroids. The emphasis will be on exposing the interplay between the graph theoretical and matroid theoretical concepts\, and no prior knowledge of matroids will be assumed. \nMatroids are often introduced either as objects that capture linear independence\, or as generalisations of graphs. If one likes to think of a matroid as a structure that captures linear independence in vector spaces\, then a delta-matroid is a structure that arises by retaining the (Steinitz) exchange properties of vector space bases\, but dropping the requirement that basis elements are all of the same size. On the other hand\, if one prefers to think of matroids as generalising graphs\, then delta-matroids generalise graphs embedded in surfaces. There are a host of other ways in which delta-matroids arise in combinatorics. Indeed\, they were introduced independently by three different groups of authors in the 1980s\, with each definition having a different motivation (and all different from the two above). \nIn this talk I’ll survey some of the ways in which delta-matroids appear in graph theory. The focus will be on how the fundamental operations on delta-matroids appear\, in different guises\, as familiar and well-studied concepts in graph theory. In particular\, I’ll illustrate how apparently disparate pieces of graph theory come together in the world of delta-matroids. \n
URL:https://dimag.ibs.re.kr/event/2020-05-12/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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BEGIN:VEVENT
DTSTART;VALUE=DATE:20200615
DTEND;VALUE=DATE:20200620
DTSTAMP:20200219T031121
CREATED:20190607T162650Z
LAST-MODIFIED:20190607T162650Z
UID:947-1592179200-1592611199@dimag.ibs.re.kr
SUMMARY:Seymour is Seventy
DESCRIPTION:A conference honouring the seventieth birthday of Paul Seymour \n\nTo be held in ENS de Lyon\, France\, June 15 – 19\, 2020 \nConference Website: https://dimag.ibs.re.kr/seymour70/ \nSponsors: \n\nIBS Discrete Mathematics Group.\nLIP\, ENS de Lyon\, France.\nDepartment of Mathematics\, Princeton University.\n\n\n
URL:https://dimag.ibs.re.kr/event/seymour-is-seventy/
LOCATION:ENS de Lyon\, Lyon\, France
CATEGORIES:Workshops and Conferences
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BEGIN:VEVENT
DTSTART;VALUE=DATE:20200824
DTEND;VALUE=DATE:20200829
DTSTAMP:20200219T031121
CREATED:20191122T084127Z
LAST-MODIFIED:20200210T223007Z
UID:1878-1598227200-1598659199@dimag.ibs.re.kr
SUMMARY:2020 IBS Workshop on Extremal and Probabilistic Combinatorics
DESCRIPTION:Date\nAugust 24\, 2020 – August 28\, 2020 \nArrival: August 23 Sunday. Departure: August 29\, Saturday \nVenue\nInstitute for Basic Science\, 55 Expo-ro\, Yuseong-gu\, Daejeon\, South Korea \nInvited Speakers\n\nJulia Böttcher\, London School of Economics\nBoris Bukh\, Carnegie Mellon University\nAmin Coja-Oghlan\, Goethe University\nDavid Conlon\, Caltech\nPenny Haxell\, University of Waterloo\nHao Huang\, Emory University\nJeff Kahn\, Rutgers University\nAlexandr V. Kostochka\, University of Illinois at Urbana-Champaign\nMichael Krivelevich\, Tel-Aviv University\nMichał Karoński\, Adam Mickiewicz University in Poznań\nAnita Liebenau\, UNSW Sydney\nHong Liu\, University of Warwick\nTomasz Łuczak\, Adam Mickiewicz University in Poznań\nRichard Montgomery\, University of Birmingham\nTobias Müller\, Groningen University\nPéter Pál Pach\, Budapest University of Technology and Economics\nMathias Schacht\, University of Hamburg\nAsaf Shapira\, Tel-Aviv University\nJoel Spencer\, New York University\nVan Vu\, Yale University\nYufei Zhao\, MIT\nThis list is incomplete. It is subject to change.\n\nAccommodation\nLotte City Hotel and Hotel ICC are within 700m. Invited speakers will be provided an accommodation at the near-by hotels. \nOrganizers\n\nMihyun Kang\, Graz University of Technology\, Austria.\nJaehoon Kim\, KAIST\, Korea.\nSang-il Oum\, IBS Discrete Mathematics Group\, Korea and KAIST\, Korea.\n\n
URL:https://dimag.ibs.re.kr/event/2020-ibs-workshop/
LOCATION:Room B234\, IBS (기초과학연구원)
CATEGORIES:Workshops and Conferences
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