기초과학연구원 이산수학그룹
On October 21, 2025, William Cook from University of Waterloo gave a talk at the Discrete Math Seminar on using branch-decompositions for discrete optimization problems, including the traveling salesman problem. The title of his talk was “Optimization via Branch Decomposition“.
On October 14, 2025, Ilkyoo Choi (최일규) from Hankuk University of Foreign Studies and IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar on the average degree of list-color-critical graphs and DP-color-critical graphs. The title of his talk was “An improved lower bound on the number of edges in list critical graphs via DP coloring“.
The IBS Discrete Mathematics Group welcomes Jigang Choi (최지강), a new graduate student of the Discrete Mathematics Group from October 1, 2025. He received his B.S. degree from Hanyang University and entered the Department of Mathematical Sciences at KAIST as a graduate student on March 2025. His advisor is Jaehoon Kim (김재훈).
On September 30, 2025, Marcelo Sales from the University of California, Irvine, gave a talk at the Discrete Math Seminar about proving lower bounds on the Ramsey numbers of some hypergraphs. His talk was titled “On the Ramsey number of Daisies and other hypergraphs.”
We are pleased to share an exciting public lecture as part of the 2025 Annual Meeting of the Korean Mathematical Society (KMS), featuring one of the world’s leading researchers in combinatorial optimization. This event is sponsored by the IBS Discrete Mathematics Group.
👤 Speaker: William Cook
🏛 Affiliation: Department of Combinatorics and Optimization, University of Waterloo
📅 Date: October 22, 2025 (Wednesday), 7:00 PM
📍 Venue: ST Center, Seoul (near Gangnam Station)
한국과학기술회관 B1, 과학기술컨벤션센터, 대회의실 2 (강남역 인근)
🗣 Language: English
🎟 Admission: Free of charge
The Traveling Salesman Problem (TSP) asks a deceptively simple question:
What is the shortest possible route that visits a set of locations exactly once and returns to the starting point?
Despite its simplicity, the TSP is a cornerstone of combinatorial optimization and theoretical computer science, long considered difficult due to its computational complexity.
In this public lecture, William Cook, a leading authority on the TSP, will discuss:
The TSP remains a central example in complexity theory, showing how sustained mathematical effort can solve problems once deemed impossible.
William Cook is a professor emeritus at the University of Waterloo and an internationally recognized expert on combinatorial optimization.
He is the author of the acclaimed book In Pursuit of the Traveling Salesman and has contributed extensively to both the theory and computation of hard optimization problems.
Whether you’re a student interested in algorithms, a researcher in discrete mathematics, or simply curious about how math solves real-world problems — this is a lecture not to be missed.
📍 Location: ST Center, Seoul
🕖 Time: 7:00 PM, Wednesday, October 22, 2025
🎟 Admission: Free | 🗣 Language: English
🔗 More info about KMS 2025 Annual Meeting
📧 For inquiries: contact@kms.or.kr
On September 22, 2025, Rong Luo from West Virginia University gave a talk at the Discrete Math Seminar on nowhere-zero flows on signed graphs. His talk was titled “Modulo flows and Integer flows of signed graphs“.
On September 16, 2025, Mujin Choi (최무진) from KAIST and the IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar on unavoidable induced minors in graphs of large tree-independence number without a fixed induced star. The title of his talk was “Excluding ladder and wheel as induced minor in graphs without induced stars“.
On September 9, 2025, Katherine Perry from the Soka University of America gave a talk at the Discrete Math Seminar on the relationship between the distinguishing number and the fixing number of trees. The title of her talk was “Symmetry breaking in trees“.
The IBS Discrete Mathematics Group (DIMAG) in Daejeon, Korea invites applications for four research fellowship positions (senior researcher positions).
DIMAG is a research group that was established on December 1, 2018 at the Institute for Basic Science (IBS), led by its Chief Investigator (CI) Sang-il Oum. DIMAG is located at the headquarters of IBS in Daejeon, South Korea, a city of 1.5 million people. Currently, DIMAG consists of researchers from various countries and the work is done in English. DIMAG is co-located with the IBS Extremal Combinatorics and Probability Group (ECOPRO).
Website : https://dimag.ibs.re.kr/
Successful candidates for the research fellowship positions will be new or recent PhDs with outstanding research potential in all fields of Discrete Mathematics with emphasis on Structural Graph Theory, Extremal Graph Theory, Combinatorial Optimization, Matroid Theory, and Algorithms.
This appointment is for about two years, and the starting salary is no less than KRW 63,000,000. The appointment is one-time renewable up to 5 years in total, contingent upon the outstanding performance of the researcher. The expected appointment date is September 1, 2026, and it can be adjusted to earlier or later, but no later than December 1, 2026. This is purely a research position and will have no teaching duties. However, if desired, successful candidates may have the opportunity to teach at KAIST.
A complete application packet should include:
1. AMS standard cover sheet (preferred) or cover letter (PDF format)
2. Curriculum vitae including a list of publications and preprints (PDF format)
3. Research statement (PDF format)
4. Consent to Collection and Use of Personal Information (form available on the application page)
5. 3 recommendation letters
For full consideration, applicants should upload items 1, 2, 3, and 4 on the application website (https://dimag.ibs.re.kr/apply) and arrange their recommendation letters to be submitted directly by the letter writers through the link sent via email during the online application process by December 3, 2025, Wednesday (Anywhere on Earth (AoE)). Recommendation letters submitted by an applicant will not be considered. DIMAG encourages applications from individuals of diverse backgrounds.
For Korean citizens who have not yet completed their military duty: 전문연구요원 종사를 희망하는 경우에는 지원 의사와 병역 관계를 cover letter 및 이메일 등에 표시하여 제출 필요. 다만 현역입영대상자의 전문연구요원 신규 편입은 불가하며, 보충역 대상자 및 타 기관에서 전직해서 오는 경우에 한하여 지원 가능(전직 요건이 충족 되어야만 함)
Inquiry: dimag _@_ ibs.re.kr (remove _)
On September 2, 2025, Zhifei Yan from the IBS Extremal Combinatorics and Probability Group gave a talk at the Discrete Math Seminar on covering the vertex set of a properly edge-colored graph with two vertex-disjoint rainbow cycles. The title of his talk was “A Rainbow version of Lehel’s conjecture“.