BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Discrete Mathematics Group - ECPv6.16.3//NONSGML v1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
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:20260519T163000
DTEND;TZID=Asia/Seoul:20260519T173000
DTSTAMP:20260611T042441
CREATED:20251215T012742Z
LAST-MODIFIED:20260511T073042Z
UID:11990-1779208200-1779211800@dimag.ibs.re.kr
SUMMARY:Xavier Goaoc\, A canonical tree decomposition for order types\, and some applications
DESCRIPTION:We introduce and study a notion of decomposition of planar point sets (or rather of their chirotopes) as trees decorated by smaller chirotopes. This decomposition is based on the concept of mutually avoiding sets (which we rephrase as modules)\, and adapts in some sense the modular decomposition of graphs in the world of chirotopes. The associated tree always exists and is unique up to some appropriate constraints. We also show how to compute the number of triangulations of a chirotope efficiently\, starting from its tree and the (weighted) numbers of triangulations of its parts. \nThis is joint work with Mathilde Bouvel\, Valentin Féray\, and Florent Koechlin.
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:20260611T042441
CREATED:20260112T025344Z
LAST-MODIFIED:20260519T011855Z
UID:12084-1779813000-1779816600@dimag.ibs.re.kr
SUMMARY:Fernanda Rivera Omaña\, Erdős-Pósa theorem for matroids
DESCRIPTION:We will look at an analogue theorem of the classical Erdős-Pósa Theorem. We prove a $GF(q)$-representable matroid analogue of Robertson and Seymour’s theorem that planar graphs have an Erdős-Pósa property. Given a matroid $N$\, we prove that for every matroid $M$ with bounded branch width\, $M$ either contains $r$ skew copies of $N$\, or there is a small perturbation of $M$ that doesn’t contain $N$ as a minor. \nThis is joint work with James Davies and Meike Hatzel.
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:20260611T042441
CREATED:20251210T144125Z
LAST-MODIFIED:20260524T215108Z
UID:11977-1780417800-1780421400@dimag.ibs.re.kr
SUMMARY:Maria Chudnovsky\, Induced minors and treewidth
DESCRIPTION:This talk deals with induced minor obstructions to treewidth. The natural setup for this problem is to consider the class of graphs excluding some planar graph\, and some complete bipartite graph as induced minors\, and some complete graph as a subgraph. Unfortunately\, such  classes still contain graphs of arbitrarily large treewidth. Moreover\, a result of Alecu\, Bonnet\, Bureo Villafana and Trotignon and its extensions suggest that there is no elegant characterization of families of bounded treewidth in terms of induced obstructions. \nOn the other hand\, it is conjectured that graphs in the classes as above have treewidth bounded by a poly-logarithmic function of their number of vertices. If true\, this will imply the existence of quasi-polynomial time algorithms for a host of problems on such  classes that are NP-complete in the general setting. \nWhile this conjecture remains open\, in joint work with Julien Codsi\, David Fischer and Daniel Lokshtanov\, we were able to prove the existence of a sub-polynomial bound on treewidth in terms of the number of vertices. This in turn leads to sub-exponential algorithmic behavior. \nIn this talk we will discuss some ideas of the proof\, and\, if time permits\, some results in the more general setting when the bound on the clique size is removed.
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:20260611T042441
CREATED:20260420T212857Z
LAST-MODIFIED:20260522T151349Z
UID:12560-1781022600-1781026200@dimag.ibs.re.kr
SUMMARY:J. Pascal Gollin\, Dominated balanced separators in wheel-induced-minor-free graphs
DESCRIPTION:The grid theorem of Robertson and Seymour can be equivalently stated using balanced separators\, that are separators whose deletion leaves every component with no more than half of the vertices of the graph\, as follows. Every graph that excludes some planar graph as a minor has a balanced separator of bounded size. Building on this formulation\, Gartland and Lokshtanov conjectured an induced minor version of that theorem inspired by coarse graph theory. They conjectured that every graph that excludes some planar graph as an induced minor has a balanced separator which is dominated by a bounded number of vertices. We confirm this conjecture for excluding any fixed wheel\, that is\, a cycle together with a universal vertex\, as an induced minor. \nThis talk is based on joint work with Maria Chudnovsky\, Matjaž Krnc\, and Martin Milanič.
URL:https://dimag.ibs.re.kr/event/2026-06-09/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260616T163000
DTEND;TZID=Asia/Seoul:20260616T173000
DTSTAMP:20260611T042441
CREATED:20260602T121956Z
LAST-MODIFIED:20260602T121956Z
UID:12717-1781627400-1781631000@dimag.ibs.re.kr
SUMMARY:Harry Richman\, Distinguishing graphs with tropical Weierstrass weights
DESCRIPTION:I will introduce a new structure on finite graphs\, which takes the form of a labeling of the vertices by nonnegative integers (possibly repeated). This labeling is isomorphism invariant\, and seems to reflect some mix of local and global structure of the graph. I will describe an algorithm for computing these labels\, which uses a form of breadth-first search\, and some results on the resulting labels. This construction comes from a tropical analogue of Weierstrass weights on algebraic curves\, studied in the 1800s. Finally\, I will discuss some speculation on whether this may or may not be helpful for the graph isomorphism problem. \nThis is a joint work with Omid Amini and Lucas Gierczak.
URL:https://dimag.ibs.re.kr/event/2026-06-16/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260619T163000
DTEND;TZID=Asia/Seoul:20260619T173000
DTSTAMP:20260611T042441
CREATED:20260515T123736Z
LAST-MODIFIED:20260610T004840Z
UID:12649-1781886600-1781890200@dimag.ibs.re.kr
SUMMARY:Stefan Weltge\, The relaxation complexity of the standard simplex is logarithmic
DESCRIPTION:For a set $X$ of integer points\, the relaxation complexity $\operatorname{rc}(X)$ is the smallest number of facets of any polyhedron P whose integer points are precisely those of X. In this paper\, we focus on the case where X is the discrete standard simplex $\Delta_d = \{0\, e_1\, …\, e_d\}$. We show that $\operatorname{rc}(\Delta_d) = O(\log d)$ by an explicit\, elementary construction. This improves upon the previously best-known upper bound $\operatorname{rc}(\Delta_d) = O(d / \sqrt{\log d})$ due to Aprile\, Averkov\, Di Summa\, and Hojny (2022) and matches an asymptotic lower bound by Averkov and Schymura (2020). This is joint work with Simon Keil.
URL:https://dimag.ibs.re.kr/event/2026-06-19/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20260628
DTEND;VALUE=DATE:20260712
DTSTAMP:20260611T042441
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:20260611T042441
CREATED:20260324T141000Z
LAST-MODIFIED:20260505T064804Z
UID:12471-1783701000-1783704600@dimag.ibs.re.kr
SUMMARY:Ting-Wei Chao\, The Oddtown Problem Modulo a Composite Number
DESCRIPTION:A family of sets in $[n]$ is called an $\ell$-Oddtown if the sizes of all sets are not divisible by $\ell$\, but the sizes of pairwise intersections are divisible by $\ell$. The problem was completely solved when $\ell$ is a prime via an elegant linear algebraic method\, showing that the family has size at most $n$. However\, not much was known for composite numbers. By splitting the family into families correspond to each prime factor of $\ell$\, one can show that the number is at most $\omega n$\, where $omega$ is the number of prime factors of $\ell$. We used both combinatorial and Fourier analytic arguments to prove that the number of sets in any $\ell$-Oddtown is at most $\omega n-(2\omega+\varepsilon)\log_2 n$ for most $n\,\ell$.
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:20260611T042441
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:20260805T163000
DTEND;TZID=Asia/Seoul:20260805T173000
DTSTAMP:20260611T042441
CREATED:20260520T141609Z
LAST-MODIFIED:20260520T141609Z
UID:12683-1785947400-1785951000@dimag.ibs.re.kr
SUMMARY:Meike Hatzel\, TBA
DESCRIPTION:
URL:https://dimag.ibs.re.kr/event/2026-08-05/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20260810
DTEND;VALUE=DATE:20260815
DTSTAMP:20260611T042441
CREATED:20260522T224718Z
LAST-MODIFIED:20260522T224718Z
UID:12688-1786320000-1786751999@dimag.ibs.re.kr
SUMMARY:2026 Summer School on Combinatorics and Algorithms (2026 조합론 및 알고리즘 여름학교)
DESCRIPTION:The 2026 Summer School on Combinatorics and Algorithms is a venue for students and early-career researchers to learn selected topics in theoretical computer science and discrete mathematics. It will be a great opportunity for young and aspiring researchers to study topics which are important but not covered during the lectures in the university classes. \nWebsite: https://combialgo.dimag.kr/2026/ \nLecturers and Topics\n\nDaniel Dadush\, CWI\, Amsterdam\n\nAlgorithms & Geometry of Linear Programming\n\n\nMagnus Wahlström\, Royal Holloway\, University of London\n\nMatroids\, delta-matroids\, and applications\n\n\n\nSchedule\n\nStart on 10 August 2026 Monday\, 2 PM\nEnd on 14 August 2025 Friday\, 5 PM
URL:https://dimag.ibs.re.kr/event/2026-08-10/
LOCATION:Bldg. E11\, KAIST
CATEGORIES:Workshops and Conferences
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20260818T163000
DTEND;TZID=Asia/Seoul:20260818T173000
DTSTAMP:20260611T042441
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
END:VCALENDAR