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“.

## Jakub Gajarský gave a talk on the class of graphs of structurally bounded expansion at the discrete math seminar

On December 10, 2019, Jakub Gajarský from Technische Universität Berlin presented a talk on the class of graphs of structurally bounded expansion and its relationship to the low shrubdepth covers. The title of his talk was “First-order interpretations of bounded expansion classes“.

## Frédéric Meunier gave a talk about new bounds on orthogonality dimension of graphs at the discrete math seminar

On November 21, 2019, Frédéric Meunier from École Nationale des Ponts et Chaussées, Paris presented a talk on the orthogonal representations and the orthogonality dimension of graphs at the discrete math seminar. The title of his talk was “Topological bounds for graph representations over any field“.

## 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.

## Tony Huynh gave a talk on the maximum weight stable set problem on graphs with bounded number of disjoint odd cycles at the Discrete Math Seminar

On November 12, Tony Huynh from Monash University gave a talk on the maximum weight stable set problem on graphs with bounded odd cycle packing number. The title of his talk was “Stable sets in graphs with bounded odd cycle packing number“.

## 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“.

## Joonkyung Lee (이준경) presented a recent work on weakly norming and norming graphs at the discrete math seminar

On October 22, 2019, Joonkyung Lee (이준경) from University of Hamburg gave a talk based on his recent work on weakly norming and norming graphs. The title of his talk was “On some properties of graph norms“.

## 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.”