2023 Vertex-Minor Workshop
2023-10-15 - 2023-10-20 | SONO BELLE Jeju
This workshop aims to foster collaborative discussions and explore the various aspects of vertex-minors, including structural theory and their applications.
This event will be small-scale, allowing for focused talks and meaningful interactions among participants.
Website: https://indico.ibs.re.kr/event/596/

The 3rd East Asia Workshop on Extremal and Structural Graph Theory
2023-11-01 - 2023-11-05 | The Southern Beach Hotel & Resort Okinawa
The 3rd East Asia Workshop on Extremal and Structural Graph Theory is a workshop to bring active researchers in the field of extremal and structural graph theory, especially in the East Asia such as China, Japan, and Korea.
Website: http://tgt.ynu.ac.jp/2023EastAsia.html

IBS-DIMAG workshop on combinatorics and geometric measure theory
2024-07-15 - 2024-07-19 | Room B109, IBS (기초과학연구원)
Website: https://cgmt.dimag.kr/
Arrival Date: July 14, 2024 Sunday.
Departure Date: July 20, 2024 Saturday.
Organizers

Ben Lund (IBS Discrete Mathematics Group)
Doowon Koh (Chungbuk National University)
Sang-il Oum (IBS Discrete Mathematics Group / KAIST)

2024 Summer School on Combinatorics and Algorithms (2024 조합론 및 알고리즘 여름학교)
2024-07-22 - 2024-07-26 | Bldg. N1, KAIST
The 2024 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. This summer, two lecture series, combinatorial optimization and grid minor theorem, will be given by two leading experts on the subjects. There will be exercise sessions where you form a team and solve challenging questions related to the lecture subjects.
Website: https://combialgo.dimag.kr/
Lecturers and Topics

Chien-Chung Huang (ENS Paris, France): Combinatorial Optimization

This lecture (12.5h) will cover essential topics in combinatorial optimization including: Berge’s theorem, Konig’s theorem, Egervary’s theorem, Karger’s min-cut algorithm and Gomory-Hu trees, Edmonds’ blossom algorithm for maximum matching, matroid 101, multi-commodity flow and k-coverage problems.

Sebastian Wiederrecht (DIMAG-IBS, Korea): From treewidth to grid minor theorem

This lecture (6h) will present the notion of tree decomposition, treewidth and graph minor, and introduce the grid minor theorem by Robertson and Seymour. Grid minor theory is deemed as one of the most important theory in modern graph theory and has many applications in algorithms design, data structure, logic, etc.

2024 Korean Student Combinatorics Workshop (KSCW2024, 2024 조합론 학생 워크샵)
2024-07-29 - 2024-08-02 | Gongju Hanok Village, Gongju
Venue
Gongju Hanok Vilage (공주한옥마을)
Organizers

Donggyu Kim (김동규), KAIST and IBS Discrete Mathematics Group
Seokbeom Kim (김석범), KAIST and IBS Discrete Mathematics Group
Seonghyuk Im (임성혁), KAIST and IBS Extremal Combinatorics and Probability Group
Hyunwoo Lee (이현우), KAIST and IBS Extremal Combinatorics and Probability Group

2024 Workshop on (Mostly) Matroids
2024-08-19 - 2024-08-23 | IBS Science Culture Center
The 2024 Workshop on (Mostly) Matroids will be held in-person at the Institute for Basic Science (IBS), Daejeon, South Korea, from August 19, 2024 to August 23, 2024. We expect that most people would arrive on Sunday, August 18 and leave on Saturday, August 24.
Our hope is that this workshop will continue the tradition of previous workshops held in Sittard (2008), Maastricht (2010,2012), Princeton (2014), Eindhoven(2016), Waterloo (2017), and Baton Rouge (2019). The focus will be on all aspects of matroid theory, including its connection to graph theory, algebraic geometry, and other areas of mathematics.

2024 Combinatorics Workshop (2024 조합론 학술대회)
2024-08-28 - 2024-08-30 | Chungbuk National University
Website: https://cw2024.combinatorics.kr/
Location
Chungbuk National University, Cheongju, Korea.
Advisory Committee

Committee of Discrete Mathematics, The Korean Mathematical Society (Chair: Sang-il Oum, IBS Discrete Mathematics Group / KAIST)

Sponsors

IBS Discrete Mathematics Group.
Korean Mathematical Society

IBS-DIMAG Workshop on Topology and Combinatorics
2024-11-11 11:00 - 17:30 (Asia/Seoul) | Room B332, IBS (기초과학연구원)
The IBS-DIMAG Workshop on Topology and Combinatorics will be held on November 11, 2024 at Room B332, Institute for Basic Science (IBS), Daejeon, South Korea.
Invited Speakers (tentative)

Karim Adiprasito (Jussieu Institute of Mathematics)
Minho Cho조민호 (IBS Extremal Combinatorics and Probability Group)
Niloufar Fuladi (INRIA Center of Université de Lorraine)
Minki Kim김민기 (GIST)
Dohyeon Lee이도현 (KAIST & IBS Discrete Mathematics Group)
Geunho Lim임근호 (Jussieu Institute of Mathematics)
Semin Yoo유세민 (IBS Discrete Mathematics Group)

Tentative Schedule

11:00-11:30 Karim Adiprasito, The Charney Davis conjecture and Boolean decompositions
12:00-14:00 Lunch Break
14:00-14:30 Niloufar Fuladi, Universal families of arcs and curves on surfaces
14:30-15:00 Semin Yoo유세민, The Charney-Davis conjecture and its related complexes (survey)
15:00-15:30 Geunho Lim임근호, Bounds on Cheeger-Gromov invariants and simplicial complexity of triangulated manifolds
15:30-16:00 Break
16:00-16:30 Minki Kim김민기, Some extensions of the colorful Helly theorem
16:30-17:00 Minho Cho조민호, Fractional Helly theorems via weak saturation
17:00-17:30 Dohyeon Lee이도현, Betti number of clique complex of H-free graphs (survey)
18:00-20:00 Banquet

Organizer

Semin Yoo유세민, IBS Discrete Mathematics Group

Abstracts
Karim Adiprasito, The Charney Davis conjecture and Boolean decompositions
I will present a novel approach to the Charney Davis conjecture by introducing anticommutative Lefschetz properties, and studying them on the Danzer complex of flag spheres.
Semin Yoo, The Charney-Davis conjecture and its related complexes (survey)
The Charney-Davis conjecture lies in the intersection between topology and combinatorics. The conjecture is a special case of the Hopf-Chern-Thurston conjecture for all nonpositively curved, piecewise Euclidean manifolds which are cellulated by regular Euclidean cubes. In 2001, Davis and Okun solved the conjecture for a 4-dimensional case, and some other partial results are also known. However, the conjecture is still open so far.
In this talk, I will describe five statements that solve the Charney-Davis conjecture and explain some complexes to achieve this goal.
Niloufar Fuladi, Universal families of arcs and curves on surfaces
In this talk I introduce a family of curves that realize all pants decomposition of a surface: a family of simple closed curves Γ on a surface realizes all types of pants decompositions if for any pants decomposition of the surface, there exists a homeomorphism sending it to a subset of the curves in Γ. The study of such universal families of curves is motivated by questions on graph embeddings, joint crossing numbers and finding an elusive center of moduli space. I will discuss the case of surfaces without punctures, where we establish an exponential upper bound and a superlinear lower bound on the minimum size of the family of curves with this universal property. I also talk about a similar concept of universality for triangulations of polygons, where we provide bounds which are tight up to logarithmic factors. In this talk, I will explain the background and context and no prior knowledge in topology or surfaces is needed.
This is joint work with Arnaud de Mesmay and Hugo Parlier.
Geunho Lim, Bounds on Cheeger-Gromov invariants and simplicial complexity of triangulated manifolds
Using L^2 cohomology, Cheeger and Gromov define the L^2 rho-invariant on manifolds with arbitrary fundamental groups, as a generalization of the Atiyah-Singer rho-invariant. There are many interesting applications in geometry, topology, and combinatorics. In this talk, we show linear bounds on the rho-invariants in terms of simplicial complexity of manifolds by using hyperbolization methods. As applications, we give new concrete examples in the complexity theory of high-dimensional (homotopy) lens spaces. This is a joint work with Shmuel Weinberger.
Minki Kim, Some extensions of the colorful Helly theorem
Given $k > d$ finite families of convex sets in $mathbb{R}^d$, if every colorful $(d+1)$-tuple is intersecting, then the union of $k-d$ color classes is intersecting. This is known as the colorful Helly theorem. Based on recent joint work with Alan Lew, I will present some extensions of the colorful Helly theorem and their applications.
Minho Cho, Fractional Helly theorems via weak saturation
Two celebrated extensions of the classical Helly’s theorem are the fractional Helly theorem and the colorful Helly theorem. Bulavka, Goodarzi, and Tancer recently established the optimal bound for the unified generalization of the fractional and the colorful Helly theorems using a colored extension of the exterior algebra. In this talk, we introduce a combinatorial reduction of both the fractional Helly theorem and its colorful version to a classical problem in extremal combinatorics known as weak saturation. No such results connecting the fractional Helly theorem and weak saturation are known in the long history of literature. These reductions, along with basic linear algebraic arguments for the reduced weak saturation problems, let us give new short proofs of the optimal bounds for both the fractional Helly theorem and its colorful version without using exterior algebra.
This is joint work with Debsoumya Chakraborti, Jinha Kim, and Minki Kim.
Dohyeon Lee, Betti number of clique complex of H-free graphs (survey)
The clique complex of a graph is a simplicial complex whose faces correspond to cliques of the given graph. In this talk, we investigate extremal properties of the Betti numbers of clique complexes. While general simplicial complexes with n vertices can have a total Betti number approximately $2^n$, Adamaszek showed that Betti number of clique complex is bounded by around $1.32^n$. Furthermore, if the underlying graph has an independence number at most two, the bound tightens to $1.25^n$. Adiprasito, Nevo, and Tancer established additional bounds on the total Betti number for clique complexes of (induced) H-free graphs for various graph H, along with constructions of graphs with large total Betti number. In another direction, Zhang and Wu demonstrated that for ternary graphs (whose with no induced cycles of length 3n), the Betti number of the independence complex (the clique complex of the complement of a graph) is at most one. Indeed, Jinha Kim showed that these independence complexes are either contractible or homotopy spheres.

IBS-DIMAG Winter School on Graph Minors, Week 1
2025-02-03 - 2025-02-05 | Room B109, IBS (기초과학연구원)

IBS-DIMAG Winter School on Graph Minors, Week 2
2025-02-10 - 2025-02-12 | Room B109, IBS (기초과학연구원)

IBS-DIMAG Winter School on Graph Minors, Week 3
2025-02-17 - 2025-02-19 | Room B109, IBS (기초과학연구원)

2025 Summer School on Combinatorics and Algorithms (2025 조합론 및 알고리즘 여름학교)
2025-07-14 14:00 - 2025-07-18 17:00 | POSTECH, Pohang, Korea
The 2025 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.
Website: https://combialgo.dimag.kr/
Lecturers and Topics

Édouard Bonnet, LIP, CNRS.

Induced Subgraphs and Induced Minors of Graphs

Michał Pilipczuk, University of Warsaw.

Structural Theory of Sparse Graphs

Schedule

Start on 14 July 2025 Monday, 2 PM
End on 18 July 2025 Friday, 5 PM

2025 Combinatorics Workshop (2025 조합론 학술대회)
2025-08-18 - 2025-08-20 | IBS Science Culture Center
Website: https://cw2025.combinatorics.kr
Invited Speakers

Dongsu Kim (KAIST)
Eun Jung Kim (KAIST)
O-joung Kwon (Hanyang University)
Ae Ja Lee (Pennsylvania State University)
Zhicong Lin (Shandong University)

Organizing Committee

Sang-il Oum (엄상일), IBS Discrete Mathematics Group
Jang Soo Kim (김장수), Sungkyunkwan University
Seunghyun Seo (서승현), Kangwon National University

2025 Korean Student Combinatorics Workshop (KSCW2025: 2025 조합론 학생 워크샵)
2025-08-20 - 2025-08-24 | The K-Hotel Gyeongju
Venue
The K-Hotel Gyeongju
Website
https://indico.ibs.re.kr/e/kscw2025
Organizers

Seokbeom Kim (김석범), KAIST and IBS Discrete Mathematics Group
Hyunwoo Lee (이현우), KAIST and IBS Extremal Combinatorics and Probability Group
Jaehyeon Seo (서재현), Yonsei University
Kyungjin Cho (조경진), POSTECH

5th East Asia Workshop on Extremal and Structural Graph Theory
2025-11-27 - 2025-11-30 | Seoul, Korea
The 5th East Asia Workshop on Extremal and Structural Graph Theory is a workshop to bring active researchers in the field of extremal and structural graph theory, especially in the East Asia such as China, Japan, and Korea.

Date
November 27, 2025 Thursday (Arrival Day) — November 30, 2025 Sunday (Departure Day)
Venue
Fraser Place Namdaemun, Seoul
Program Book
Invited Speakers

Shinya Fujita (Yokohama City University)
Jie Han (Beijing Institute of Technology)
Tony Huynh (IBS Discrete Mathematics Group)
Jaehoon Kim (KAIST)
O-joung Kwon (Hanyang University / IBS Discrete Mathematics Group)
Hong Liu (IBS Extremal Combinatorics and Probability Group)
Jie Ma (University of Science and Technology of China / Tsinghua University)
Shun-ichi Maezawa (Nihon University)
Boram Park (Seoul National University)
Shohei Satake (Kumamoto University)
Tuan Tran (University of Science and Technology of China)
Shoichi Tsuchiya (Senshu University)
Xuding Zhu (Zhejiang Normal University)

Organizers
Seog-Jin Kim, Sang-il Oum, Kenta Ozeki, Hehui Wu
Registration
Invitation Only. https://indico.ibs.re.kr/event/1041/
There is no registration fee and one dinner (banquet) will be provided.
History

4th East Asia Workshop on Extremal and Structural Graph Theory

Mar. 27 – Mar. 31, 2025.
School of Mathematics, Sun-Yet Sen University, Guangzhou, China
Organizers: Ping Hu, Seog-Jin Kim, Kenta Ozeki, Hehui Wu.

3rd East Asia Workshop on Extremal and Structural Graph Theory

Nov. 1- Nov. 5, 2023.
The Southern Beach Hotel & Resort, Okinawa, Japan
Sponsored by the IBS Discrete Mathematics Group, Korea.
Organizers: Seog-Jin Kim, Sang-il Oum, Kenta Ozeki, Hehui Wu.

2nd East Asia Workshop on Extremal and Structural Graph Theory

Oct. 31-Nov. 4, 2019.
Held at UTOP UBLESS Hotel, Jeju, Korea
Sponsored by the IBS Discrete Mathematics Group, Korea.
Organizers: Seog-Jin Kim, Sang-il Oum, Kenta Ozeki, Hehui Wu.

1st East Asia Workshop on Extremal and Structural Graph Theory

Nov. 30-Dec. 2, 2018.
Held and sponsored by the Shanghai Center for Mathematical Sciences in China, under the name 2018 SCMS Workshop on Extremal and Structural Graph Theory.
Organizers: Ping Hu, Seog-Jin Kim, Kenta Ozeki, Hehui Wu.

Thursday
November 27, 2025

Time
Speaker
Affiliation
Title

16:00–18:00

Registration & Discussions

Friday
November 28, 2025

Time
Speaker
Affiliation
Title

09:20–10:00
Jaehoon Kim
KAIST
Hamilton cycles in pseudorandom graphs: Dirac’s theorem and approximate decompositions

10:00–10:30

Coffee Break

10:30–11:10
Jie Ma
University of Science and Technology of China / Tsinghua University
An exponential improvement for Ramsey lower bounds

11:20–12:00
Shinya Fujita
Yokohama City University
Connectivity keeping paths containing prescribed vertices in highly connected triangle-free graphs

12:00–14:00

Lunch Break

14:00–14:40
Shun-ichi Maezawa
Nihon University
Tree versus tree of preorder induced by rainbow forbidden subgraphs

14:50–15:30
Tony Huynh
IBS Discrete Mathematics Group
Rainbow triangles and the Erdős–Hajnal problem in projective geometries

15:30–15:50

Coffee Break

16:30–17:30

Problem Session

Saturday
November 29, 2025

Time
Speaker
Affiliation
Title

09:20–10:00
Xuding Zhu
Zhejiang Normal University
TBA

10:00–10:30

Coffee Break

10:30–11:10
Hong Liu
IBS Extremal Combinatorics and Probability Group
Chromatic, homomorphism, blowup thresholds and beyond

11:20–12:00
Shohei Satake
Kumamoto University
TBA

12:00–14:00

Lunch Break

14:00–14:40
Shoichi Tsuchiya
Senshu University
On the number of contractible edges in plane triangulations

14:50–15:30
Tuan Tran
University of Science and Technology of China
Littlewood-Offord bounds on the symmetric groups and applications

15:30–15:50

Coffee Break

15:50–16:30
O-joung Kwon
Hanyang University / IBS Discrete Mathematics Group
A coarse Erdős–Pósa theorem

16:30–17:30

Problem Session

18:30–21:00

Banquet

Sunday
November 30, 2025

Time
Speaker
Affiliation
Title

10:00–10:40
Jie Han
Beijing Institute of Technology
Perturbation of dense graphs

10:40–10:50

Break

10:50–11:30
Boram Park
Seoul National University
Graphs avoiding cycles of length 0 modulo 4

11:30–12:00

Closing

2026 Workshop on Topological Combinatorics
2026-06-28 - 2026-07-11 | GIST
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.
The 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).
The 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.
The campus offers a variety of amenities, including a guesthouse that can accommodate approximately 20 guests.
In addition, various lodging options are available within a 15–20 minute walking distance.
We are planning to provide accommodation for all invited participants, and we are also considering offering partial travel support for those with limited funding.

Website: https://sites.google.com/view/2026topocomb

2026 Korean Student Combinatorics Workshop
2026-07-27 - 2026-07-31 | Gongju Hanok Village, Gongju
Website: https://kscw.combinatorics.kr/

2026 Summer School on Combinatorics and Algorithms (2026 조합론 및 알고리즘 여름학교)
2026-08-10 - 2026-08-14 | Bldg. E11, KAIST
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.
Website: https://combialgo.dimag.kr/2026/
Lecturers and Topics

Daniel Dadush, CWI, Amsterdam

Algorithms & Geometry of Linear Programming

Magnus Wahlström, Royal Holloway, University of London

Matroids, delta-matroids, and applications

Schedule

Start on 10 August 2026 Monday, 2 PM
End on 14 August 2025 Friday, 5 PM

2026 Combinatorics Workshop (2026 조합론 학술대회)
2026-10-20 - 2026-10-22 | Konjiam Resort, EW Village, B2, Meeting Room OPUS2
Combinatorics Workshop (조합론 학술대회) is an annual conference for researchers in combinatorics and related areas in Korea. It was started in 2004 by the Yonsei University BK21 Research Group. Since 2013, this workshop has been advised by the committee of discrete mathematics of the Korean Mathematical Society.
Website: https://cw2026.combinatorics.kr/en/
Venue
Konjiam Resort, EW Village, B2, Meeting Room OPUS2
(278, Docheogwit-Ro, Docheok-Myeon, Gwangju-Si, Gyeonggi-Do, Korea)

Travel Instructions

Dates
October 20 to 22, 2026
Plenary Speaker
Alexander V. Kostochka (UIUC)
Invited Speakers

Cheolwon Heo (SUNY Korea)
Tony Huynh (IBS DIMAG)
Dabeen Lee (Seoul National University)
Jongbaek Song (Pusan National University)

Contributed Talks
Each contributed talk will be about 20 minutes, including questions. Please note that we may stop accepting contributed talk applications before the deadline if all available slots are filled.
If you are interested in giving a contributed talk at the workshop, please submit an abstract by August 31, 2026.
To apply for a contributed talk, go to Call for Abstracts on Indico and click “Submit new abstract.” You may need to create an IBS Indico account.
Registration
Registration link
The registration deadline is August 31, 2026.
Organizing Committee

Ilkyoo Choi (최일규), Hankuk University of Foreign Studies, IBS Discrete Mathematics Group, KIAS
Sang-il Oum (엄상일), IBS Discrete Mathematics Group
Boram Park (박보람), Seoul National University

Advisory Committee
Committee of Discrete Mathematics, The Korean Mathematical Society (Chair: Sang-il Oum)
Sponsors

IBS Discrete Mathematics Group
Korean Mathematical Society
Seoul National University
Hankuk University of Foreign Studies
