## Hong Liu gave a talk on the conjecture of Mader about the topological minors in C4-free graphs at the discrete math seminar

On December 12, 2019, Hong Liu from University of Warwick gave a talk on the resolution of the conjecture of Mader on the existence of a complete topological minor under the condition of average degree for C4-free graphs at the discrete math seminar held at KAIST. The title of his talk was “A proof of Mader’s conjecture on large clique subdivisions in $C_4$-free graphs“.

## Ruth Luo gave a talk on the induced Turán-type problems for hypergraphs at the discrete math seminar

On November 19, 2019, Ruth Luo from University of California San Diego gave a talk on the Turán-type results on r-uniform hypergraphs without a certain structure called an induced Berge-F. The title of her talk was “Induced Turán problems for hypergraphs“. She is visiting IBS discrete mathematics group until November 22.

## Dabeen Lee received the INFORMS Optimization Society Student Paper Prize on October 20, 2019

On October 20, 2019, Dabeen Lee (이다빈), a research fellow at the IBS discrete mathematics group, received the 2nd place prize in the INFORMS Optimization Society Student Paper Prize. This prize was established in 2006 by the Optimization Society of the Institute for Operations Research and the Management Sciences and is awarded annually at the INFORMS Annual Meeting for the most outstanding paper in optimization. This year, the INFORMS Annual Meeting was held in Seattle, USA.

Dabeen was awarded for the paper co-authored with his Ph.D. advisor Prof. Gérard Cornuéjols, titled “On some polytopes contained in the 0,1 hypercube that have a small Chvátal rank“. This paper was published in Mathematical Programming in November 2018.

## DIMAG hosted “The 2nd East Asia Workshop on Extremal and Structural Graph Theory” at Jeju

From October 31 to November 4, 2019, IBS discrete mathematics group hosted the 2nd East Asia Workshop on Extremal and Structural Graph Theory in Jeju. It 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. Participants have great chance to discuss recent progress in graph theory, interesting open problems, finding new potential collaborators, and exploring the beautiful island.

## Invited Speakers

• Ping Hu, Sun Yat-Sen University, China
• Jaehoon Kim, KAIST, Korea
• O-joung Kwon, Incheon National University and IBS Discrete Mathematics Group, Korea
• Joonkyung Lee, University of Hamburg, Germany
• Binlong Li, Northwestern Polytechnical University, China
• Hongliang Lu, Xi’an Jiaotong University, China
• Abhishek Methuku, IBS Discrete Mathematics Group, Korea
• Atsuhiro Nakamoto, Yokohama National University, Japan
• Kenta Noguchi, Tokyo University of Science, Japan
• Kenta Ozeki, Yokohama National University, Japan
• Boram Park, Ajou University, Korea
• Yuejian Peng, Hunan University, China
• Zi-Xia Song, University of Central Florida, U.S.A.
• Tomáš Kaiser, University of West Bohemia, Czech Republic.
• Maho Yokota, Tokyo University of Science, Japan.
• Xuding Zhu, Zhejiang Normal University, China

## Participants

 Toshiki Abe Yokohama National University Jungho Ahn KAIST / IBS Discrete Mathematics Group Sejeong Bang Yeungnam University Ilkyoo Choi Hankook University of Foreign Studies Jeong Ok Choi GIST Shinya Fujita Yokohama City University Alexander Gavrilyuk Pusan National University Pascal Gollin IBS Discrete Mathematics Group Kevin Hendrey IBS Discrete Mathematics Group Ping Hu Sun Yat-sen University Tomáš Kaiser University of West Bohemia Dong Yeap Kang KAIST / IBS Discrete Mathematics Group Gen Kawatani Tokyo University of Science Donggyu Kim KAIST / IBS Discrete Mathematics Group Jaehoon Kim KAIST Jeong Han Kim KIAS Ringi Kim KAIST Seog-Jin Kim Konkuk University Younjin Kim Ewha Womans University O-joung Kwon Incheon National University / IBS Discrete Mathematics Group Young Soo Kwon Yeungnam University Dabeen Lee IBS Discrete Mathematics Group Duksang Lee KAIST / IBS Discrete Mathematics Group Joonkyung Lee University of Hamburg Sang June Lee Kyung Hee University Hui Lei Nankai University Binlong Li Northwestern Polytechnical University Henry Liu Sun Yat-sen University Hongliang Lu Xi’an Jiaotong University Jie Ma University of Science and Technology of China Yulai Ma Nankai University Ryota Matsubara Shibaura Institute of Technology Abhishek Methuku IBS Discrete Mathematics Group Atsuhiro Nakamoto Yokohama National University Kenta Noguchi Tokyo University of Science Suil O SUNY-Korea Sang-il Oum IBS Discrete Mathematics Group / KAIST Kenta Ozeki Yokohama National University Boram Park Ajou University Jongyook Park Kyungpook National University Yuejian Peng Hunan University Yoshio Sano University of Tsukuba Yongtang Shi Nankai University Mark Siggers Kyungpook National University Zi-Xia Song University of Central Florida Casey Tompkins IBS Discrete Mathematics Group Guanghui Wang Shandong University Douglas West Zhejiang Normal University Hehui Wu Shanghai Center for Mathematical Sciences Maho Yokota Tokyo U Science Xin Zhang Xidian University Xuding Zhu Zhejiang Normal University

## Organizers

• Seog-Jin Kim, Konkuk University, Korea.
• Sang-il Oum, IBS Discrete Mathematics Group, Korea and KAIST, Korea.
• Kenta Ozeki, Yokohama National University, Japan.
• Hehui Wu, Shanghai Center for Mathematical Sciences, China.

## Pascal Gollin gave a talk on the existence of a decomposition of an infinite graph into spanning trees at the discrete math seminar

On October 29, 2019, Pascal Gollin from IBS discrete mathematics group gave a talk on the existence of a decomposition of an infinite graph into spanning trees in terms of the existence of packing and covering of spanning trees at the discrete math seminar. The title of his talk was “A Cantor-Bernstein-type theorem for spanning trees in infinite graphs“.

## Zi-Xia Song (宋梓霞) gave a talk on Ramsey numbers under Gallai colorings at the discrete math seminar

On October 15, 2019, Prof Zi-Xia Song (宋梓霞) from University of Central Florida (UCF) presented a talk about Ramsey numbers under Gallai colorings. The title of her talk was “Ramsey numbers of cycles under Gallai colorings.”