On August 9, 2023, the 2023 Mini-Workshop on Discrete Geometry was held at the IBS. This workshop consisted of three talks by Michael Dobbins from SUNY Binghamton, Andreas Holmsen from KAIST, and Minki Kim from GIST. Here is the list of talks.

Michael Dobbins (SUNY Binghamton): Colorful intersections, Tverberg partitions, and geometric transversals

Andreas Holmsen (KAIST): The topology of the complex of ordered partitions

Minki Kim^{김민기} (GIST): Some variants of the colorful Helly theorems

On February 23, 2021, Minki Kim (김민기) from the IBS discrete mathematics group presented a talk on the existence of a rainbow matching of size n in a family of 3n-3 matchings for n>2 at the Discrete Math Seminar. The title of his talk was “Rainbow paths and rainbow matchings“.

We prove that if $n \geq 3$, then any family of $3n-3$ sets of matchings of size $n$ in any graph has a rainbow matching of size $n$. This improves on a previous result, in which $3n-3$ is replaced by $3n-2$. We also prove a “cooperative” generalization: for $t > 0$ and $n \geq 3$, any $3n-4+t$ sets of edges, the union of every $t$ of which contains a matching of size $n$, have rainbow matching of size $n$. This is joint work with Ron Aharoni, Joseph Briggs, and Jinha Kim.

On September 29, 2020, Minki Kim (김민기) from the IBS Discrete Mathematics Group presented his work on the collapsibility of the complex $I_n(G)$ of vertex sets of a graph $G$ not containing any $n$-vertex independent set at the Discrete Math Seminar. The title of his talk was “Complexes of graphs with bounded independence number“.

Let $G$ be a graph on $V$ and $n$ a positive integer. Let $I_n(G)$ be the abstract simplicial complex whose faces are the subsets of $V$ that do not contain an independent set of size $n$ in $G$. We study the collapsibility numbers of $I_n(G)$ for various classes of graphs, focusing on the class of graphs with bounded maximum degree. This is joint work with Alan Lew.

The IBS Discrete Mathematics Group welcomes Dr. Jinha Kim (김진하) and Dr. Minki Kim (김민기), new research fellows at the IBS Discrete Mathematics Group from September 1, 2020.

Jinha Kim (김진하) received his Ph.D. from the Department of Mathematics at Seoul National University in 2019 under the supervision of Prof. Woong Kook. Until recently, she was a postdoctoral fellow at Technion in Israel. She is interested in combinatorics, discrete geometry, topological combinatorics, and graph theory.

Minki Kim (김민기) received his Ph.D. from the Department of Mathematical Sciences at KAIST in 2018 under the supervision of Prof. Andreas Holmsen. Until recently, he was a postdoctoral fellow at Technion in Israel. He is interested in discrete geometry, topological combinatorics, and graph theory.