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PRODID:-//Discrete Mathematics Group - ECPv5.1.5//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:20200902T163000
DTEND;TZID=Asia/Seoul:20200902T173000
DTSTAMP:20200808T111130
CREATED:20200708T123031Z
LAST-MODIFIED:20200708T123031Z
UID:2619-1599064200-1599067800@dimag.ibs.re.kr
SUMMARY:Sebastian Siebertz\, Rank-width meets stability
DESCRIPTION:Forbidden graph characterizations provide a convenient way of specifying graph classes\, which often exhibit a rich combinatorial and algorithmic theory. A prime example in graph theory are classes of bounded tree-width\, which are characterized as those classes that exclude some planar graph as a minor. Similarly\, in model theory\, classes of structures are characterized by configurations that are forbidden as logical interpretations or transductions. Two notions from classical model theory are (monadic) stability and (monadic) dependence\, which correspond to the impossibility of interpreting with first-order logic (after a vertex coloring step) arbitrary long linear orders and all graphs\, respectively. Examples of monadically stable classes of graphs are nowhere dense graph classes\, and examples of monadically dependent classes are classes of bounded rank-width (or equivalently\, bounded clique-width)\, which can be seen as a dense analog of classes of bounded tree-width. \nI will give an overview over recent approaches to combine model theoretic and graph theoretic tools to derive structural and algorithmic results for classes of (finite) graphs. I assume no background from logic. \n
URL:https://dimag.ibs.re.kr/event/2020-09-02/
LOCATION:Zoom
CATEGORIES:Virtual Discrete Math Colloquium
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200826T103000
DTEND;TZID=Asia/Seoul:20200826T113000
DTSTAMP:20200808T111130
CREATED:20200629T004929Z
LAST-MODIFIED:20200710T062805Z
UID:2576-1598437800-1598441400@dimag.ibs.re.kr
SUMMARY:Nick Brettell\, TBA
DESCRIPTION:
URL:https://dimag.ibs.re.kr/event/2020-08-26/
LOCATION:Zoom
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200824
DTEND;VALUE=DATE:20200825
DTSTAMP:20200808T111130
CREATED:20200804T150044Z
LAST-MODIFIED:20200804T150044Z
UID:2758-1598227200-1598313599@dimag.ibs.re.kr
SUMMARY:2020 Combinatorics Workshop
DESCRIPTION:Combinatorics Workshop (조합론 학술대회) is the biggest annual conference in combinatorics in Korea. It was firstly held in 2004 by the Yonsei University BK21 Research Group. It has been advised by the committee of discrete mathematics of the Korean Mathematical Society since 2013. The aim of this workshop is to bring active researchers with different backgrounds to discuss recent and prospective advances in combinatorics and related areas. \nOriginally\, we planned an offline workshop. However\, COVID 19 is more spreading and many participants are worried about attending an offline conference. So the schedule and venue are changed as an online workshop with Zoom and as a small offline workshop at Kyung Hee University only with speakers and organizers. I hope that all participants generously understand this sudden change. \nInvited Speakers\n\nSejeong Bang (방세정)\, Yeungnam University\nRingi Kim (김린기)\, KAIST\nSangwook Kim (김상욱)\, Chonnam National University\nJinyoung Park (박진영)\, Institute for Advanced Study\nJongyook Park (박종육)\, Kyungpook N. University\n\nContributed speakers\n\nByung-Hak Hwang (황병학)\, Seoul National University\nJaeseong Oh (오재성)\, Seoul National University\nJun Seok Oh (오준석)\, Incheon National University\nTuan Tran\, Institute for Basic Science (IBS)\n\n
URL:https://dimag.ibs.re.kr/event/2020-combinatorics-workshop/
LOCATION:Kyung Hee University (경희대학교) – Space21 B110\, Seoul\, Korea\, Republic of
CATEGORIES:Workshops and Conferences
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BEGIN:VEVENT
DTSTART;VALUE=DATE:20200824
DTEND;VALUE=DATE:20200829
DTSTAMP:20200808T111130
CREATED:20191122T084127Z
LAST-MODIFIED:20200427T082500Z
UID:1878-1598227200-1598659199@dimag.ibs.re.kr
SUMMARY:2020 IBS Workshop on Extremal and Probabilistic Combinatorics (postponed)
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
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200819T163000
DTEND;TZID=Asia/Seoul:20200819T173000
DTSTAMP:20200808T111130
CREATED:20200629T004729Z
LAST-MODIFIED:20200702T014301Z
UID:2573-1597854600-1597858200@dimag.ibs.re.kr
SUMMARY:Gwenaël Joret\, Packing and covering balls in graphs excluding a minor
DESCRIPTION:In 2007\, Chepoi\, Estellon\, and Vaxès conjectured that there exists a universal constant $c>0$ such that the following holds for every positive integers $r$ and $k$\, and every planar graph $G$: Either $G$ contains $k$ vertex-disjoint balls of radius $r$\, or there is a subset of vertices of size at most $c k$ meeting all balls of radius $r$ in $G$. The key aspect of this conjecture is that the constant $c$ does not depend on the radius $r$ of the balls. If we were to allow this dependency\, then the statement is known to hold\, and in fact it is true in the more general setting of graph classes with bounded expansion (as proved by Dvořák). \nIn this talk I will present a proof of this conjecture. The result we prove is a bit more general: (1) The conjecture holds for every proper minor-closed class of graphs (with the constant $c$ depending on the class)\, and (2) we can even focus on any set of balls in the graph we like\, there is nothing special about taking all balls of a given radius. In other words\, we show that for every proper minor-closed class $C$ of graphs\, there exists a constant $c>0$ such that for every graph $G$ in $C$\, every set $S$ of balls in $G$\, and every positive integer $k$\, either there are $k$ vertex-disjoint balls in $S$\, or there is a subset of vertices of $G$ of size at most $c k$ meeting all balls in $S$. \nJoint work with Nicolas Bousquet\, Wouter Cames van Batenburg\, Louis\nEsperet\, William Lochet\, Carole Muller\, and François Pirot. \n
URL:https://dimag.ibs.re.kr/event/2020-08-19/
LOCATION:Zoom
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200818T163000
DTEND;TZID=Asia/Seoul:20200818T173000
DTSTAMP:20200808T111130
CREATED:20200804T124550Z
LAST-MODIFIED:20200804T124550Z
UID:2750-1597768200-1597771800@dimag.ibs.re.kr
SUMMARY:Tuan Tran\, Anti-concentration phenomena
DESCRIPTION:Let $X$ be a real random variable; a typical anti-concentration inequality asserts that (under certain assumptions) if an interval $I$ has small length\, then $\mathbb{P}(X\in I)$ is small\, regardless the location of $I$. Inequalities of this type have found powerful applications in many branches of mathematics. In this talk we will discuss several recent applications of anti-concentration inequalities in extremal combinatorics\, as well as random matrix theory. The talk is partially based on joint work with Matthew Kwan and Benny Sudakov. \n
URL:https://dimag.ibs.re.kr/event/2020-08-18/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200811T163000
DTEND;TZID=Asia/Seoul:20200811T173000
DTSTAMP:20200808T111130
CREATED:20200725T052636Z
LAST-MODIFIED:20200725T052636Z
UID:2708-1597163400-1597167000@dimag.ibs.re.kr
SUMMARY:Yunbum Kook (국윤범)\, Vertex Sparsification for Edge Connectivity
DESCRIPTION:Graph compression or sparsification is a basic information-theoretic and computational question. A major open problem in this research area is whether $(1+\epsilon)$-approximate cut-preserving vertex sparsifiers with size close to the number of terminals exist. As a step towards this goal\, we initiate the study of a thresholded version of the problem: for a given parameter $c$\, find a smaller graph\, which we call connectivity-$c$ mimicking network\, which preserves connectivity among $k$ terminals exactly up to the value of $c$. We show that contraction-based connectivity-$c$ mimicking networks with $O(kc^4)$ edges exist by (1) introducing an extension of well-linkedness to a thresholded $c$-connectivity setting and (2) leveraging a kernelization result\, based on gammoid and the representative sets lemma\, to identify `essential edges’ in minimum edge cuts between a partition of terminals. We also develop an algorithm based on expander decomposition\, which can find a contraction-based $c$-mimicking network of the optimal size in $m(c\log n)^{O(c)}$. \nThese results lead to the first data structures for answering fully dynamic offline $c$-edge-connectivity queries for $c \ge 4$ in polylogarithmic time per query\, as well as more efficient algorithms for survivable network design on bounded treewidth graphs. \nThis is a joint work with Parinya Chalermsook\, Syamantak Das\, Bundit Laekhanukit\, Yang P. Liu\, Richard Peng\, Mark Sellke\, and Daniel Vaz. \n
URL:https://dimag.ibs.re.kr/event/2020-08-11/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200810
DTEND;VALUE=DATE:20200814
DTSTAMP:20200808T111130
CREATED:20200221T012853Z
LAST-MODIFIED:20200427T014651Z
UID:2145-1597017600-1597363199@dimag.ibs.re.kr
SUMMARY:Nonlinear Algebra in Daejeon (Postponed)
DESCRIPTION:Program\n\nSummer School @ KAIST (August 4-7\, 2020)\nDiscussion Weekend (August 8-9\, 2020)\nWorkshop @ IBS Science Culture Center (August 10-13\, 2020)\n\nWebsite: https://dimag.ibs.re.kr/home/nonlinear/ \nOrganizing Committee\n\nInsong Choe (Konkuk U.)\nKangjin Han (DGIST)\nDavid Hyeon (SNU)\nSijong Kwak (KAIST)\nYongnam Lee (KAIST)\nAnton Leykin (Georgia Tech)\nSang-il Oum (IBS & KAIST)\nFrank Sottile (TAMU)\n\n
URL:https://dimag.ibs.re.kr/event/nonlinear-algebra-in-daejeon/
LOCATION:IBS Science Culture Center
CATEGORIES:Workshops and Conferences
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