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PRODID:-//Discrete Mathematics Group - ECPv6.15.20//NONSGML v1.0//EN
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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:20190101T000000
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201022T101000
DTEND;TZID=Asia/Seoul:20201022T111000
DTSTAMP:20260418T155756
CREATED:20200927T024614Z
LAST-MODIFIED:20240705T194022Z
UID:3056-1603361400-1603365000@dimag.ibs.re.kr
SUMMARY:Chun-Hung Liu (劉俊宏)\, Asymptotic dimension of minor-closed families and beyond
DESCRIPTION:The asymptotic dimension of metric spaces is an important notion in  geometric group theory. The metric spaces considered in this talk are  the ones whose underlying spaces are the vertex-sets of (edge-)weighted  graphs and whose metrics are the distance functions in weighted graphs.  A standard compactness argument shows that it suffices to consider the  asymptotic dimension of classes of finite weighted graphs. We prove that  the asymptotic dimension of any minor-closed family of weighted graphs\,  any class of weighted graphs of bounded tree-width\, and any class of  graphs of bounded layered tree-width are at most 2\, 1\, and 2\,  respectively. The first result solves a question of Fujiwara and  Papasoglu; the second and third results solve a number of questions of  Bonamy\, Bousquet\, Esperet\, Groenland\, Pirot and Scott. These bounds for  asymptotic dimension are optimal and generalize and improve some results  in the literature\, including results for Riemannian surfaces and Cayley  graphs of groups with a forbidden minor.
URL:https://dimag.ibs.re.kr/event/2020-10-22/
LOCATION:Zoom ID:95464969835 (356260)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201021T163000
DTEND;TZID=Asia/Seoul:20201021T173000
DTSTAMP:20260418T155756
CREATED:20200930T112510Z
LAST-MODIFIED:20240707T082519Z
UID:3085-1603297800-1603301400@dimag.ibs.re.kr
SUMMARY:Joonkyung Lee (이준경)\, On graph norms for complex-valued functions
DESCRIPTION:For any given graph $H$\, one may define a natural corresponding functional $\|.\|_H$ for real-valued functions by using homomorphism density. One may also extend this to complex-valued functions\, once $H$ is paired with a $2$-edge-colouring $\alpha$ to assign conjugates. We say that $H$ is real-norming (resp. complex-norming) if $\|.\|_H$ (resp. there is $\alpha$ such that $\|.\|_{H\,\alpha}$) is a norm on the vector space of real-valued (resp. complex-valued) functions. This generalises Gowers norms\, a widely used tool in extremal combinatorics to quantify quasirandomness. \nWe unify these two seemingly different notions of graph norms in real- and complex-valued settings\, by proving that $H$ is complex-norming if and only if it is real-norming. Our proof does not explicitly construct a suitable $2$-edge-colouring $\alpha$ but obtain its existence and uniqueness\, which may be of independent interest. \nAs an application\, we give various example graphs that are not norming. In particular\, we show that hypercubes are not norming\, which answers the only question appeared in Hatami’s pioneering work in the area that remained untouched. This is joint work with Alexander Sidorenko.
URL:https://dimag.ibs.re.kr/event/2020-10-21/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201015T170000
DTEND;TZID=Asia/Seoul:20201015T180000
DTSTAMP:20260418T155756
CREATED:20200915T062234Z
LAST-MODIFIED:20240705T194121Z
UID:2982-1602781200-1602784800@dimag.ibs.re.kr
SUMMARY:Hong Liu (刘鸿)\, Cycles and trees in graphs (8/8)
DESCRIPTION:This lecture series covers several different techniques on embedding paths/trees/cycles in (pseudo)random graphs/expanders as (induced) subgraphs.
URL:https://dimag.ibs.re.kr/event/2020-10-15/
LOCATION:Zoom ID:8628398170 (123450)
CATEGORIES:Online Lecture Series
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201014T170000
DTEND;TZID=Asia/Seoul:20201014T180000
DTSTAMP:20260418T155756
CREATED:20200915T062130Z
LAST-MODIFIED:20240705T194123Z
UID:2980-1602694800-1602698400@dimag.ibs.re.kr
SUMMARY:Hong Liu (刘鸿)\, Cycles and trees in graphs (7/8)
DESCRIPTION:This lecture series covers several different techniques on embedding paths/trees/cycles in (pseudo)random graphs/expanders as (induced) subgraphs.
URL:https://dimag.ibs.re.kr/event/2020-10-14/
LOCATION:Zoom ID:8628398170 (123450)
CATEGORIES:Online Lecture Series
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201013T170000
DTEND;TZID=Asia/Seoul:20201013T180000
DTSTAMP:20260418T155756
CREATED:20200915T062032Z
LAST-MODIFIED:20240705T194124Z
UID:2978-1602608400-1602612000@dimag.ibs.re.kr
SUMMARY:Hong Liu (刘鸿)\, Cycles and trees in graphs (6/8)
DESCRIPTION:This lecture series covers several different techniques on embedding paths/trees/cycles in (pseudo)random graphs/expanders as (induced) subgraphs.
URL:https://dimag.ibs.re.kr/event/2020-10-13/
LOCATION:Zoom ID:8628398170 (123450)
CATEGORIES:Online Lecture Series
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201012T170000
DTEND;TZID=Asia/Seoul:20201012T180000
DTSTAMP:20260418T155756
CREATED:20200915T061926Z
LAST-MODIFIED:20240705T194125Z
UID:2976-1602522000-1602525600@dimag.ibs.re.kr
SUMMARY:Hong Liu (刘鸿)\, Cycles and trees in graphs (5/8)
DESCRIPTION:This lecture series covers several different techniques on embedding paths/trees/cycles in (pseudo)random graphs/expanders as (induced) subgraphs.
URL:https://dimag.ibs.re.kr/event/2020-10-12/
LOCATION:Zoom ID:8628398170 (123450)
CATEGORIES:Online Lecture Series
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201008T170000
DTEND;TZID=Asia/Seoul:20201008T180000
DTSTAMP:20260418T155756
CREATED:20200915T061756Z
LAST-MODIFIED:20240705T194127Z
UID:2974-1602176400-1602180000@dimag.ibs.re.kr
SUMMARY:Hong Liu (刘鸿)\, Cycles and trees in graphs (4/8)
DESCRIPTION:This lecture series covers several different techniques on embedding paths/trees/cycles in (pseudo)random graphs/expanders as (induced) subgraphs.
URL:https://dimag.ibs.re.kr/event/2020-10-08/
LOCATION:Zoom ID:8628398170 (123450)
CATEGORIES:Online Lecture Series
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201007T170000
DTEND;TZID=Asia/Seoul:20201007T180000
DTSTAMP:20260418T155756
CREATED:20200915T061653Z
LAST-MODIFIED:20240705T194128Z
UID:2971-1602090000-1602093600@dimag.ibs.re.kr
SUMMARY:Hong Liu (刘鸿)\, Cycles and trees in graphs (3/8)
DESCRIPTION:This lecture series covers several different techniques on embedding paths/trees/cycles in (pseudo)random graphs/expanders as (induced) subgraphs.
URL:https://dimag.ibs.re.kr/event/2020-10-07/
LOCATION:Zoom ID:8628398170 (123450)
CATEGORIES:Online Lecture Series
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201006T170000
DTEND;TZID=Asia/Seoul:20201006T180000
DTSTAMP:20260418T155756
CREATED:20200915T060857Z
LAST-MODIFIED:20240705T194130Z
UID:2969-1602003600-1602007200@dimag.ibs.re.kr
SUMMARY:Hong Liu (刘鸿)\, Cycles and trees in graphs (2/8)
DESCRIPTION:This lecture series covers several different techniques on embedding paths/trees/cycles in (pseudo)random graphs/expanders as (induced) subgraphs.
URL:https://dimag.ibs.re.kr/event/2020-10-06/
LOCATION:Zoom ID:8628398170 (123450)
CATEGORIES:Online Lecture Series
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20201005T170000
DTEND;TZID=Asia/Seoul:20201005T180000
DTSTAMP:20260418T155756
CREATED:20200915T060706Z
LAST-MODIFIED:20240705T194131Z
UID:2967-1601917200-1601920800@dimag.ibs.re.kr
SUMMARY:Hong Liu (刘鸿)\, Cycles and trees in graphs (1/8)
DESCRIPTION:This lecture series covers several different techniques on embedding paths/trees/cycles in (pseudo)random graphs/expanders as (induced) subgraphs.
URL:https://dimag.ibs.re.kr/event/2020-10-05/
LOCATION:Zoom ID:8628398170 (123450)
CATEGORIES:Online Lecture Series
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200929T163000
DTEND;TZID=Asia/Seoul:20200929T173000
DTSTAMP:20260418T155756
CREATED:20200921T045326Z
LAST-MODIFIED:20240705T194112Z
UID:3014-1601397000-1601400600@dimag.ibs.re.kr
SUMMARY:Minki Kim (김민기)\, Complexes of graphs with bounded independence number
DESCRIPTION:Let $G$ be a graph on $V$ and $n$ a positive integer. Let $I_n(G)$ be the abstract simplicial complex whose faces are the subsets of $V$ that do not contain an independent set of size $n$ in $G$. We study the collapsibility numbers of $I_n(G)$ for various classes of graphs\, focusing on the class of graphs with bounded maximum degree. This is joint work with Alan Lew.
URL:https://dimag.ibs.re.kr/event/2020-09-29/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200924T100000
DTEND;TZID=Asia/Seoul:20200924T110000
DTSTAMP:20260418T155756
CREATED:20200811T231744Z
LAST-MODIFIED:20240707T082720Z
UID:2781-1600941600-1600945200@dimag.ibs.re.kr
SUMMARY:Zihan Tan\, Towards Tight(er) Bounds for the Excluded Grid Theorem
DESCRIPTION:We study the Excluded Grid Theorem\, a fundamental structural result in graph theory\, that was proved by Robertson and Seymour in their seminal work on graph minors. The theorem states that there is a function $f$\, such that for every integer $g > 0$\, every graph of treewidth at least $f(g)$ contains the g×g-grid as a minor. For every integer $g > 0$\, let $f(g)$ be the smallest value for which the theorem holds. Establishing tight bounds on $f(g)$ is an important graph-theoretic question. Robertson and Seymour showed that f(g) is at least of order $g^2 \log g$. For a long time\, the best known upper bounds on $f(g)$ were super-exponential in $g$. The first polynomial upper bound of $f(g) = O(g^{98} \operatorname{poly log} g)$ was proved by Chekuri and Chuzhoy. It was later improved to $f(g) = O(g^{36} \operatorname{poly log} g)$\, and then to $f(g) = O(g^{19} \operatorname{poly log} g)$. In this talk\, we present our recent work that further improves this bound to $f(g) = O(g^9 \operatorname{poly log} g)$ via a simpler proof. Moreover\, while there are natural barriers that seem to prevent the previous methods from yielding tight bounds for the theorem\, it seems conceivable that the techniques proposed in this talk can lead to even tighter bounds on $f(g)$. \nThis talk is based on joint work with Julia Chuzhoy.
URL:https://dimag.ibs.re.kr/event/2020-09-24/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200922T163000
DTEND;TZID=Asia/Seoul:20200922T173000
DTSTAMP:20260418T155756
CREATED:20200914T065243Z
LAST-MODIFIED:20240707T082727Z
UID:2960-1600792200-1600795800@dimag.ibs.re.kr
SUMMARY:Jinha Kim (김진하)\, Collapsibility of Non-Cover Complexes of Graphs
DESCRIPTION:Let $G$ be a graph on the vertex set $V$. A vertex subset $W \subset V$ is a cover of $G$ if $V \setminus W$ is an independent set of $G$\, and $W$ is a non-cover of $G$ if $W$ is not a cover of $G$. The non-cover complex of $G$ is a simplicial complex on $V$ whose faces are non-covers of $G$. Then the non-cover complex of $G$ is the combinatorial Alexander dual of the independence complex of $G$. In this talk\, I will show the $(|V(G)|-i\gamma(G)-1)$-collapsibility of the non-cover complex of a graph $G$ where $i\gamma(G)$ denotes the independence domination number of $G$ using the minimal exclusion sequence method. This is joint work with Ilkyoo Choi and Boram Park.
URL:https://dimag.ibs.re.kr/event/2020-09-22/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200917T100000
DTEND;TZID=Asia/Seoul:20200917T110000
DTSTAMP:20260418T155756
CREATED:20200811T231948Z
LAST-MODIFIED:20240707T082734Z
UID:2789-1600336800-1600340400@dimag.ibs.re.kr
SUMMARY:Luke Postle\, Further progress towards Hadwiger's conjecture
DESCRIPTION:In 1943\, Hadwiger conjectured that every graph with no $K_t$ minor is $(t-1)$-colorable for every $t\ge 1$. In the 1980s\, Kostochka and Thomason independently proved that every graph with no $K_t$ minor has average degree $O(t\sqrt{\log t})$ and hence is $O(t\sqrt{\log t})$-colorable.  Recently\, Norin\, Song and I showed that every graph with no $K_t$ minor is $O(t(\log t)^{\beta})$-colorable for every $\beta > 1/4$\, making the first improvement on the order of magnitude of the $O(t\sqrt{\log t})$ bound. Here we show that every graph with no $K_t$ minor is $O(t (\log t)^{\beta})$-colorable for every $\beta > 0$; more specifically\, they are $O(t (\log \log t)^{6})$-colorable.
URL:https://dimag.ibs.re.kr/event/2020-09-17/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200915T163000
DTEND;TZID=Asia/Seoul:20200915T173000
DTSTAMP:20260418T155756
CREATED:20200901T083403Z
LAST-MODIFIED:20240705T194142Z
UID:2919-1600187400-1600191000@dimag.ibs.re.kr
SUMMARY:Debsoumya Chakraborti\, Maximum number of cliques in a graph with bounded maximum degree
DESCRIPTION:Generalized extremal problems have been one of the central topics of study in extremal combinatorics throughout the last few decades. One such simple-looking problem\, maximizing the number of cliques of a fixed order in a graph with a fixed number of vertices and given maximum degree\, was recently resolved by Chase. Settling a conjecture of Kirsch and Radcliffe\, we resolve the edge variant of this problem\, where the number of edges is fixed instead of the number of vertices. This talk will be based on joint work with Da Qi Chen.
URL:https://dimag.ibs.re.kr/event/2020-09-15/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200910T171000
DTEND;TZID=Asia/Seoul:20200910T181000
DTSTAMP:20260418T155756
CREATED:20200708T123031Z
LAST-MODIFIED:20240705T200015Z
UID:2619-1599757800-1599761400@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.
URL:https://dimag.ibs.re.kr/event/2020-09-10/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200908T163000
DTEND;TZID=Asia/Seoul:20200908T173000
DTSTAMP:20260418T155756
CREATED:20200820T123810Z
LAST-MODIFIED:20240705T194152Z
UID:2831-1599582600-1599586200@dimag.ibs.re.kr
SUMMARY:Rutger Campbell\, Disasters in abstracting combinatorial properties of linear dependence
DESCRIPTION:Let E be a finite set and I be a collection of subsets of E. When is there a set of real vectors indexed by E such that I correspond to its linearly independent subsets? In 1935\, Whitney introduced matroids using some necessary conditions for this. However\, complete characterizations with various techniques are intractable. This remains the case even if it is already known that there is a set of complex vectors indexed by E whose collection of linearly independent subsets corresponds to I.
URL:https://dimag.ibs.re.kr/event/2020-09-08/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200901T103000
DTEND;TZID=Asia/Seoul:20200901T113000
DTSTAMP:20260418T155756
CREATED:20200825T130632Z
LAST-MODIFIED:20240707T082809Z
UID:2855-1598956200-1598959800@dimag.ibs.re.kr
SUMMARY:Junguk Lee (이정욱)\, A quick introduction to stability and NIP: Part III. NIP
DESCRIPTION:I give a quick survey on stability and NIP(Non-Independent Property). We first review basic facts on the first order logic and give some historical remarks on classification theory in model theory. We review basic properties of stability and NIP. Finally\, we aim to give several characterizations of stability and NIP of a given formula in terms of counting types and definability types.
URL:https://dimag.ibs.re.kr/event/2020-09-01/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200831T161500
DTEND;TZID=Asia/Seoul:20200831T171500
DTSTAMP:20260418T155756
CREATED:20200825T130503Z
LAST-MODIFIED:20240707T082818Z
UID:2851-1598890500-1598894100@dimag.ibs.re.kr
SUMMARY:Junguk Lee (이정욱)\, A quick introduction to stability and NIP: Part II. Stability
DESCRIPTION:I give a quick survey on stability and NIP(Non-Independent Property). We first review basic facts on the first order logic and give some historical remarks on classification theory in model theory. We review basic properties of stability and NIP. Finally\, we aim to give several characterizations of stability and NIP of a given formula in terms of counting types and definability types.
URL:https://dimag.ibs.re.kr/event/2020-08-31-part2/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200831T150000
DTEND;TZID=Asia/Seoul:20200831T160000
DTSTAMP:20260418T155756
CREATED:20200825T130214Z
LAST-MODIFIED:20240707T082829Z
UID:2848-1598886000-1598889600@dimag.ibs.re.kr
SUMMARY:Junguk Lee (이정욱)\, A quick introduction to stability and NIP: Part I. Basic first order logic
DESCRIPTION:I give a quick survey on stability and NIP(Non-Independent Property). We first review basic facts on the first order logic and give some historical remarks on classification theory in model theory. We review basic properties of stability and NIP. Finally\, we aim to give several characterizations of stability and NIP of a given formula in terms of counting types and definability types.
URL:https://dimag.ibs.re.kr/event/2020-08-31/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200826T103000
DTEND;TZID=Asia/Seoul:20200826T113000
DTSTAMP:20260418T155756
CREATED:20200629T004929Z
LAST-MODIFIED:20240705T200027Z
UID:2576-1598437800-1598441400@dimag.ibs.re.kr
SUMMARY:Nick Brettell\, On the graph width parameter mim-width
DESCRIPTION:Maximum induced matching width\, also known as mim-width\, is a width parameter for graphs introduced by Vatshelle in 2012.  This parameter can be defined over branch decompositions of a graph G\, where the width of a vertex partition (X\,Y) in G is the size of a maximum induced matching in the bipartite graph induced by edges of G with one endpoint in X and one endpoint in Y.  In this talk\, I will present a quick overview of mim-width and some key results that highlight why this parameter is of interest from both a theoretical and algorithmic point of view.  I will discuss some recent work regarding the boundedness or unboundedness of mim-width for hereditary classes defined by forbidding one or two induced subgraphs\, and for generalisations of convex graphs.  I will also touch on some interesting applications of this work\, in particular for colouring and list-colouring.  This is joint work with Jake Horsfield\, Andrea Munaro\, Giacomo Paesani\, and Daniel Paulusma.
URL:https://dimag.ibs.re.kr/event/2020-08-26/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200825T163000
DTEND;TZID=Asia/Seoul:20200825T173000
DTSTAMP:20260418T155756
CREATED:20200816T234618Z
LAST-MODIFIED:20240707T082841Z
UID:2794-1598373000-1598376600@dimag.ibs.re.kr
SUMMARY:Ben Lund\, Point-plane incidence bounds
DESCRIPTION:In the early 1980s\, Beck proved that\, if P is a set of n points in the real plane\, and no more than g points of P lie on any single line\, then there are $\Omega(n(n-g))$ lines that each contain at least 2 points of P. In 2016\, I found a generalization of this theorem\, giving a similar lower bound on the number of planes spanned by a set of points in real space. I will discuss this result\, along with a number of applications and related open problems.
URL:https://dimag.ibs.re.kr/event/2020-08-25/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200824
DTEND;VALUE=DATE:20200829
DTSTAMP:20260418T155756
CREATED:20191122T084127Z
LAST-MODIFIED:20240705T203020Z
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.
URL:https://dimag.ibs.re.kr/event/2020-ibs-workshop/
LOCATION:Room B234\, IBS (기초과학연구원)
CATEGORIES:Workshops and Conferences
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200824
DTEND;VALUE=DATE:20200825
DTSTAMP:20260418T155756
CREATED:20200804T150044Z
LAST-MODIFIED:20240705T195125Z
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. 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\nMore information is available on the website https://cw2020.combinatorics.kr.
URL:https://dimag.ibs.re.kr/event/2020-combinatorics-workshop/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Workshops and Conferences
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200819T163000
DTEND;TZID=Asia/Seoul:20200819T173000
DTSTAMP:20260418T155756
CREATED:20200629T004729Z
LAST-MODIFIED:20240705T200030Z
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.
URL:https://dimag.ibs.re.kr/event/2020-08-19/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200818T163000
DTEND;TZID=Asia/Seoul:20200818T173000
DTSTAMP:20260418T155756
CREATED:20200804T124550Z
LAST-MODIFIED:20240707T082915Z
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.
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:20260418T155756
CREATED:20200725T052636Z
LAST-MODIFIED:20240707T082925Z
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.
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:20260418T155756
CREATED:20200221T012853Z
LAST-MODIFIED:20240705T201209Z
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)
URL:https://dimag.ibs.re.kr/event/nonlinear-algebra-in-daejeon/
LOCATION:IBS Science Culture Center
CATEGORIES:Workshops and Conferences
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200805T163000
DTEND;TZID=Asia/Seoul:20200805T173000
DTSTAMP:20260418T155756
CREATED:20200629T004613Z
LAST-MODIFIED:20240705T200032Z
UID:2570-1596645000-1596648600@dimag.ibs.re.kr
SUMMARY:Robert Ganian\, Solving Integer Linear Programs by Exploiting Variable-Constraint Interactions
DESCRIPTION:Integer Linear Programming (ILP) is among the most successful and general paradigms for solving computationally intractable optimization problems in computer science. ILP is NP-complete\, and until recently we have lacked a systematic study of the complexity of ILP through the lens of variable-constraint interactions. This changed drastically in recent years thanks to a series of results that together lay out a detailed complexity landscape for the problem centered around the structure of graphical representations of instances. The aim of this talk is to summarize these recent developments and put them into context. Special attention will be paid to the structural parameter treedepth\, and at the end of the talk we will also consider how treedepth can be used to design algorithms for problems beyond ILP.
URL:https://dimag.ibs.re.kr/event/2020-08-05/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20200804T163000
DTEND;TZID=Asia/Seoul:20200804T173000
DTSTAMP:20260418T155756
CREATED:20200708T124259Z
LAST-MODIFIED:20240705T200010Z
UID:2626-1596558600-1596562200@dimag.ibs.re.kr
SUMMARY:June Huh (허준이)\, Kazhdan-Lusztig polynomials of graphs and matroids
DESCRIPTION:I will introduce Kazhdan-Lusztig polynomials of matroids and survey combinatorial and geometric theories built around them. The focus will be on the conjecture of Gedeon\, Proudfoot\, and Young that all zeros of the Kazhdan-Lusztig polynomial of a matroid lie on the negative real axis.
URL:https://dimag.ibs.re.kr/event/2020-08-04/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
END:VCALENDAR