Discrete Mathematics Group

Ting-Wei Chao, The Oddtown Problem Modulo a Composite Number
2026-07-10 16:30 - 17:30 (Asia/Seoul) | Room B332, IBS (기초과학연구원)
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 $omega n-(2omega+varepsilon)log_2 n$ for most $n,ell$.

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

Meike Hatzel, TBA
2026-08-05 16:30 - 17:30 | Room B332, IBS (기초과학연구원)

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

Jinyoung Park (박진영), TBA
2026-08-18 16:30 - 17:30 | Room B332, IBS (기초과학연구원)
