On May 17, 2023, Szymon Toruńczyk from the University of Warsaw gave an online talk at the Virtual Discrete Math Colloquium, introducing the flip-width of graphs at the Virtual Discrete Math Colloquium. The title of his talk was “Flip-width: Cops and Robber on dense graphs.”

## Oliver Janzer gave a talk on finding a subgraph of large average degree on a small vertex set at the Discrete Math Seminar

On May 16, 2023, Oliver Janzer from the University of Cambridge gave a talk at the Discrete Math Seminar on finding a subgraph of large average degree on a small vertex set at the Discrete Math Seminar. The title of his talk was “small subgraphs with large average degree.”

## The MATRIX-IBS Workshop “Structural Graph Theory Downunder III” was held from April 17 to April 23

The MATRIX-IBS Workshop “Structural Graph Theory Downunder III” was held from April 17, 2023 to April 23, 2023 at Creswick, Victoria, Australia. This program is supported by MATRIX and the Discrete Mathematics Group (DIMAG) of the Institute for Basic Science (IBS, Korea). MATRIX is a residential research institute for the mathematical sciences in Australia.

## Participants

- Rutger Campbell (IBS Discrete Mathematics Group, Korea)
- Linda Cook (IBS Discrete Mathematics Group, Korea)
- James Davies (University of Cambridge, UK)
- Marc Distel (Monash University, Australia)
- Zdeněk Dvořák (Charles University, Czech Republic)
- Bryce Frederickson (Emory University, USA)
- António Girão (University of Oxford, UK)
- Pascal Gollin (IBS Discrete Mathematics Group, Korea)
- Kevin Hendrey (IBS Discrete Mathematics Group, Korea)
- Robert Hickingbotham (Monash University, Australia)
- Freddie Illingworth (University of Oxford, UK)
- O-joung Kwon (Hanyang University and IBS Discrete Mathematics Group, Korea)
- Florian Lehner (University of Auckland, New Zealand)
- Anita Liebenau (UNSW, Australia)
- Chun-Hung Liu (Texas A&M, USA)
- Rose McCarty (Princeton University, USA)
- Lukas Michel (University of Oxford, UK)
- Sang-il Oum (IBS Discrete Mathematics Group and KAIST, Korea)
- Michael Savery (University of Oxford, UK)
- Alex Scott (University of Oxford, UK)
- Raphael Steiner (ETH Zurich, Switzerland)
- Jane Tan (University of Oxford, UK)
- Sebastian Wiederrecht (IBS Discrete Mathematics Group, Korea)
- David Wood (Monash University, Australia)
- Liana Yepremyan (Emory University, USA)

## Organizers

- David Wood (Monash University, Australia)
- Sang-il Oum (IBS Discrete Mathematics Group and KAIST, Korea)
- Alex Scott (University of Oxford, UK)
- Liana Yepremyan (Emory University, USA)

## Maria Chudnovsky gave a colloquium talk on bounding the tree-width by forbidding induced subgraphs

On May 11, 2023, Maria Chudnovsky from Princeton University gave a colloquium talk held at KAIST about bounding the tree-width of graphs by forbidding induced subgraphs. The titlte of her talk was “Induced subgraphs and tree decompositions.”

## Jozef Skokan gave a talk on finding a collection of paths such that for every pair e, f of edges, the collection has a path having e but not f at the Discrete Math Seminar

On May 9, 2023, Jozef Skokan from LSE gave a talk at the Discrete Math Seminar on finding a collection of linearly many paths such that for every pair e, f of distinct edges, there is a path having e but not f in the collection. The title of his talk was “Separating the edges of a graph by a linear number of paths.”

## Welcome Louann Coste, a visiting graduate student in the Discrete Mathematics Group from the ENS Lyon

The IBS Discrete Mathematics Group welcomes Louann Coste, a visiting graduate student from the ENS Lyon, Lyon, France. She is planning to stay with us until August 2, 2023.

## Rob Morris gave a talk showing the sketch of the proof that the diagonal Ramsey number is less than (4-𝜀)^k at the Discrete Math Seminar

During the Discrete Math Seminar held on May 2, 2023, Rob Morris of IMPA presented on the recent breakthrough regarding the diagonal Ramsey number, specifically demonstrating that $R(k,k)<(4-\varepsilon)^k$. The title of his talk was “An exponential improvement for diagonal Ramsey.”

## Welcome Chong Shangguan and Yisai Xue, long-term visitors to ECOPRO

The IBS Discrete Mathematics Group welcomes Chong Shangguan and Yisai Xue, two long-term visitors to ECOPRO group.

Chong Shangguan (上官冲) is a professor at Shandong University and will stay with us for 3 months.

Yisai Xue is a graduate student at Shanghai University and will stay with us for 1 year.

## Nika Salia organized a special session “Extremal Combinatorics: Methods and Applications” at the 2023 KMS Spring Meeting on April 28-29

On April 28-29, 2023, Nika Salia of the IBS Extremal Combinatorics and Probability Group organized a special session called “Extremal Combinatorics: Methods and Applications” at the 2023 KMS Spring Meeting held at Daejeon Convention Center, Daejeon, Korea. Here is a list of 16 talks.

⋅ 28th-A-09:00 − 09:20 Domination inequalities and dominating graphs (David Conlon, **Joonkyung Lee**)

⋅ 28th-A-09:20 − 09:40 C5-critical series parallel graphs (Eun-Kyung Cho, Ilkyoo Choi, Boram Park, **Mark H. Siggers**)

⋅ 28th-A-09:50 − 10:10 On the extremal problems related to Szemeredi’s theorem (**Younjin Kim**)

⋅ 28th-A-10:10 − 10:30 Bounds on maximum directed cut (**Jiangdong Ai**, Stefanie Gerke, Gregory Gutin, Anders Yeo, Yacong Zhou)

⋅ 28th-B-10:50 − 11:10 Rainbow cycles in edge-colored graphs (Joonkyung Lee, **Jaehoon Kim**, Hong Liu, Tuan Tran)

⋅ 28th-B-11:10 − 11:30 How connectivity affects the extremal number of trees (**Suyun Jiang**, Hong Liu, Nika Salia)

⋅ 28th-B-11:40 − 12:00 Many Hamiltonian subsets in large graphs with given density (Stijn Cambie, **Jun Gao**, Hong Liu)

⋅ 28th-B-12:00 − 12:20 Maximum total distance of hypergraphs (**Stijn Cambie**, Ervin Győri, Nika Salia, Casey Tompkins, James Tuite)

⋅ 28th-C-13:30 − 13:50 Intersection patterns and incidence theorems (Thang Pham, **Semin Yoo**)

⋅ 28th-C-13:50 − 14:10 Note on the quotient set of the quadratic distance set over finite fields (**Doowon Koh**)

⋅ 28th-C-14:20 − 14:40 Convexity and chi-boundedness (**Andreas Holmsen**)

⋅ 28th-C-14:40 − 15:00 Exceptional projections in finite vector spaces (**Ben Lund**)

⋅ 29th-D-09:00 − 09:20 Rainbow bandwidth theorem (Debsoumya Chakraborti, **Seonghyuk Im**, Jaehoon Kim, Hong Liu)

⋅ 29th-D-09:20 − 09:40 Covering multigraphs with bipartite graphs (**Hyunwoo Lee**)

⋅ 29th-D-09:50 − 10:10 Rainbow oriented Hamiltonian paths and cycles in tournaments (Debsoumya Chakraborti, Jaehoon Kim, Hyunwoo Lee, **Jaehyeon Seo**)

⋅ 29th-D-10:10 − 10:30 Colorful Hamilton cycles in random graphs (**Debsoumya Chakraborti**, Alan Frieze, Mihir Hasabnis)

## Rob Morris gave a colloquium talk at KAIST on Ramsey Theory

On April 27, 2023, Rob Morris from IMPA gave a colloquium talk on Ramsey Theory at the Colloquium of KAIST Mathematical Sciences. The title of his talk was “Ramsey theory: searching for order in chaos.” Rob Morris is currently visiting IBS and will give a seminar talk at IBS on May 2 with more details on his latest theorem on diagonal Ramsey numbers.