BEGIN:VCALENDAR
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PRODID:-//Discrete Mathematics Group - ECPv6.15.20//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
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:20250101T000000
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260428T163000
DTEND;TZID=Asia/Seoul:20260428T173000
DTSTAMP:20260416T023406
CREATED:20260303T004153Z
LAST-MODIFIED:20260303T004338Z
UID:12388-1777393800-1777397400@dimag.ibs.re.kr
SUMMARY:Xin Wei\, Separating hash families with large universe
DESCRIPTION:Separating hash families are useful combinatorial structures that generalize several well-studied objects in cryptography and coding theory. Let $p_t(N\, q)$ denote the maximum size of the universe for a $t$-perfect hash family of length $N$ over an alphabet of size $q$. We show that $q^{2 – o(1)} < p_t(t\, q) = o(q^2)$ for all  $t \ge 3$\, thereby resolving an open problem raised by Blackburn et al. (2008) for certain parameter ranges. Previously\, this result was known only for $t = 3$ and $t = 4$. Our approach establishes the existence of a large set of integers that avoids nontrivial solutions to a system of correlated linear equations. This is joint work with Xiande Zhang and Gennian Ge.
URL:https://dimag.ibs.re.kr/event/2026-04-28/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260506T163000
DTEND;TZID=Asia/Seoul:20260506T173000
DTSTAMP:20260416T023406
CREATED:20260313T150340Z
LAST-MODIFIED:20260403T110615Z
UID:12435-1778085000-1778088600@dimag.ibs.re.kr
SUMMARY:Maximilian Gorsky\, The Disjoint Paths Problem lies in the Oort cloud of algorithms
DESCRIPTION:In this talk we discuss recent work to that establishes that the bounds of the Vital Linkage Function is single-exponential. This has immediate impacts on the complexity of the k-Disjoint Paths Problem\, Minor Checking\, and more generally\, the Folio-Problem. We in fact prove something even stronger: It turns out that it is not in fact the number of terminals (or more generally vertices) that matters in these problems\, but rather their structure within the graph. Concretely\, we show that the Vital Linkage Function is single-exponential only in the bidimensionality of the terminals\, whilst the number of terminals contributes only polynomially. A direct consequence of this is an algorithm for the k-Disjoint Paths Problem running in $f(k)n^2$-time\, where f(k) is singly exponential in k and doubly exponential in the bidimensionality of k. This derives directly from an algorithm for the Folio-problem we give that has an analogous runtime. Notably these are the first algorithms for these problems in which the function f is explicit. In particular\, we give the first explicit bounds for the Vital Linkage Function. \nJoint work with Dario Cavallaro\, Stephan Kreutzer\, Dimitrios Thilikos\, and Sebastian Wiederrecht.
URL:https://dimag.ibs.re.kr/event/2026-05-06/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260512T163000
DTEND;TZID=Asia/Seoul:20260512T173000
DTSTAMP:20260416T023406
CREATED:20260320T061938Z
LAST-MODIFIED:20260407T022605Z
UID:12453-1778603400-1778607000@dimag.ibs.re.kr
SUMMARY:Benjamin Duhamel\, Excluding a forest induced minor
DESCRIPTION:We give an induced counterpart of the Forest Minor theorem: for any t ≥ 2\, the $K_{t\,t}$-subgraph-free H-induced-minor-free graphs have bounded pathwidth if and only if H belongs to a class F of forests\, which we describe as the induced minors of two (very similar) infinite parameterized families. This constitutes a significant step toward classifying the graphs H for which every weakly sparse H-induced-minor-free class has bounded treewidth. Our work builds on the theory of constellations developed in the Induced Subgraphs and Tree Decompositions series. \nThis is a joint work with É. Bonnet and R. Hickingbotham.
URL:https://dimag.ibs.re.kr/event/2026-05-12/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260519T163000
DTEND;TZID=Asia/Seoul:20260519T173000
DTSTAMP:20260416T023406
CREATED:20251215T012742Z
LAST-MODIFIED:20251215T012742Z
UID:11990-1779208200-1779211800@dimag.ibs.re.kr
SUMMARY:Xavier Goaoc\, TBA
DESCRIPTION:
URL:https://dimag.ibs.re.kr/event/2026-05-19/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260526T163000
DTEND;TZID=Asia/Seoul:20260526T173000
DTSTAMP:20260416T023406
CREATED:20260112T025344Z
LAST-MODIFIED:20260122T105556Z
UID:12084-1779813000-1779816600@dimag.ibs.re.kr
SUMMARY:Sarah Morell\, Unsplittable Transshipments
DESCRIPTION:We consider an arc-capacitated directed graph $D=(V\,A)$\, where each node $v$ is associated with a rational balance value $b(v)$. Nodes with negative balance values are referred to as sources\, while those with positive balance values are called sinks. A feasible $b$-transshipment is a flow $f : A \to \mathbb{R}_{\ge 0}$ that routes the total supply of the sources to the sinks through $D$\, while respecting the given arc capacity constraints and satisfying the balance requirements at each node. An unsplittable $b$-transshipment additionally requires that\, for each source-sink pair\, the flow sent from that source to that sink is routed along at most one directed path. Unsplittable $b$-transshipments (UT) generalize the well-studied single source unsplittable flow (SSUF) problem in which $D$ contains a single source and multiple sinks\, and each demand must be routed along a single path from the common source to its destination.  \nGiven a feasible $b$-transshipment $f$ that is not necessarily unsplittable\, a natural question is whether there exists an feasible unsplittable $b$-transshipment flow $g$ that approximates $f$ in an arc-wise sense. In particular\, we seek bounds on the maximum deviation $|f_a-g_a|$ over all arcs $a \in A$. For the special case of SSUFs\, Dinitz\, Garg\, and Goemans (Combinatorica 1999) proved that there exists an unsplittable flow $g$ such that $g_a \leq f_a + d_{\max}$ for all $a \in A$\, where $d_{\max}$ denotes the maximum demand value. Jointly with Martin Skutella (Mathematical Programming 2022)\, we studied unsplittable flows with arc-wise lower bounds and showed that there exists an unsplittable flow $g$ satisfying $g_a \ge f_a – d_{\max}$ for all $a \in A$. \n In this talk\, we extend this line of research by adapting the techniques of Dinitz\, Garg\, and Goemans to the more general setting of UTs. We show that\, given any feasible $b$-transshipment $f$\, there exists a feasible unsplittable $b$-transshipment $g$ such that $g_a \leq f_a + d_{\max}$ (resp. $g_a \ge f_a – d_{\max}$) for all $a \in A$.  \n This is joint work with Srinwanti Debgupta and Martin Skutella.
URL:https://dimag.ibs.re.kr/event/2026-05-26/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260602T163000
DTEND;TZID=Asia/Seoul:20260602T173000
DTSTAMP:20260416T023406
CREATED:20251210T144125Z
LAST-MODIFIED:20251225T223707Z
UID:11977-1780417800-1780421400@dimag.ibs.re.kr
SUMMARY:Maria Chudnovsky\, TBA
DESCRIPTION:
URL:https://dimag.ibs.re.kr/event/2025-06-02/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260609T163000
DTEND;TZID=Asia/Seoul:20260609T173000
DTSTAMP:20260416T023406
CREATED:20260122T084352Z
LAST-MODIFIED:20260122T084352Z
UID:12117-1781022600-1781026200@dimag.ibs.re.kr
SUMMARY:Martin Milanič\, TBA
DESCRIPTION:
URL:https://dimag.ibs.re.kr/event/2026-06-09/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20260628
DTEND;VALUE=DATE:20260712
DTSTAMP:20260416T023406
CREATED:20260415T104127Z
LAST-MODIFIED:20260415T104444Z
UID:12537-1782604800-1783814399@dimag.ibs.re.kr
SUMMARY:2026 Workshop on Topological Combinatorics
DESCRIPTION:The 2026 Workshop on Topological Combinatorics will be held from June 28 to July 11\, 2026 at Gwangju Institute of Science and Technology (GIST)\, located in Gwangju in the southwest of Republic of Korea.  \nThe workshop aims to bring together researchers interested in applications of topology to combinatorics and related areas. This will be the fifth workshop in a series initiated by Ron Aharoni (August 2018 in Shantou\, July 2019 in Prague\, July 2020 on Zoom\, and June 2024 in Paris). \nThe first week (June 28 – July 04) will be reserved for presentations\, while the following days (July 05 – July 11) will be for discussion and collaborations.  \nThe campus offers a variety of amenities\, including a guesthouse that can accommodate approximately 20 guests. \nIn addition\, various lodging options are available within a 15–20 minute walking distance. \nWe are planning to provide accommodation for all invited participants\, and we are also considering offering partial travel support for those with limited funding. \n\nWebsite: https://sites.google.com/view/2026topocomb
URL:https://dimag.ibs.re.kr/event/2026-06-28/
LOCATION:GIST
CATEGORIES:Workshops and Conferences
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260710T163000
DTEND;TZID=Asia/Seoul:20260710T173000
DTSTAMP:20260416T023406
CREATED:20260324T141000Z
LAST-MODIFIED:20260326T130309Z
UID:12471-1783701000-1783704600@dimag.ibs.re.kr
SUMMARY:Ting-Wei Chao\, Entropy method and mixture bound
DESCRIPTION:The entropy method has been used in many recent works in extremal combinatorics. With the help of Shannon entropy\, significant progress has been made on several classical problems\, such as the union-closed conjecture and the Sidorenko conjecture. In our recent work\, we use the entropy method to give new proofs of the Kruskal–Katona theorem and Turán’s theorem\, as well as some of their generalizations. The new ingredient in our approach is a method for upper bounding the sum of $2^{\mathbb{H}(X_i)}$  for random variables $X_1\,\cdots\,X_k$ whose supports do not overlap too much. We call this method the mixture bound\, and it can be viewed as an entropic version of double counting. In this talk\, I will introduce the mixture bound and show some examples of how it can be applied on colorful versions of the Kruskal–Katona theorem. Base on joint work with Maya Sankar and Hung-Hsun Hans Yu.
URL:https://dimag.ibs.re.kr/event/2026-07-10/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20260727
DTEND;VALUE=DATE:20260801
DTSTAMP:20260416T023406
CREATED:20260415T104353Z
LAST-MODIFIED:20260415T104353Z
UID:12545-1785110400-1785542399@dimag.ibs.re.kr
SUMMARY:2026 Korean Student Combinatorics Workshop
DESCRIPTION:Website: https://kscw.combinatorics.kr/
URL:https://dimag.ibs.re.kr/event/2026-07-27/
LOCATION:Gongju Hanok Village\, Gongju
CATEGORIES:Workshops and Conferences
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260818T163000
DTEND;TZID=Asia/Seoul:20260818T173000
DTSTAMP:20260416T023406
CREATED:20260326T020259Z
LAST-MODIFIED:20260326T020259Z
UID:12486-1787070600-1787074200@dimag.ibs.re.kr
SUMMARY:Jinyoung Park (박진영)\, TBA
DESCRIPTION:
URL:https://dimag.ibs.re.kr/event/2026-08-18/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
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