## February 2023

### Meike Hatzel, Fixed-Parameter Tractability of Directed Multicut with Three Terminal Pairs Parametrised by the Size of the Cutset: Twin-Width Meets Flow-Augmentation

Room B332 IBS (기초과학연구원)

We show fixed-parameter tractability of the Directed Multicut problem with three terminal pairs (with a randomized algorithm). This problem, given a directed graph $G$, pairs of vertices (called terminals) $(s_1,t_1)$,

### Maya Sankar, The Turán Numbers of Homeomorphs

Room B332 IBS (기초과학연구원)

Let $X$ be a 2-dimensional simplicial complex. Denote by $\text{ex}_{\hom}(n,X)$ the maximum number of 2-simplices in an $n$-vertex simplicial complex that has no sub-simplicial complex homeomorphic to $X$. The asymptotics

## March 2023

### Eunjin Oh (오은진), Parameterized algorithms for the planar disjoint paths problem

Room B332 IBS (기초과학연구원)

Given an undirected planar graph $G$ with $n$ vertices and a set $T$ of $k$ pairs $(s_i,t_i)_{i=1}^k$ of vertices, the goal of the planar disjoint paths problem is to find

### Stijn Cambie, Recent progress on the Union-closed conjecture and related

Room B332 IBS (기초과학연구원)

We give a summary on the work of the last months related to Frankl's Union-Closed conjecture and its offsprings. The initial conjecture is stated as a theorem in extremal set

### Younjin Kim (김연진), Problems on Extremal Combinatorics

Room B332 IBS (기초과학연구원)

Extremal Combinatorics studies the maximum or minimum size of finite objects (numbers, sets, graphs) satisfying certain properties. In this talk, I introduce the conjectures I solved on Extremal Combinatorics, and

### Tianchi Yang, On the maximum number of edges in k-critical graphs

Room B332 IBS (기초과학연구원)

In this talk, we will discuss the problem of determining the maximum number of edges in an n-vertex k-critical graph. A graph is considered k-critical if its chromatic number is

## April 2023

### István Tomon, Configurations of boxes

Room B332 IBS (기초과학연구원)

Configurations of axis-parallel boxes in $\mathbb{R}^d$ are extensively studied in combinatorial geometry. Despite their perceived simplicity, there are many problems involving their structure that are not well understood. I will

### James Davies, Two structural results for pivot-minors

Room B332 IBS (기초과학연구원)

Pivot-minors can be thought of as a dense analogue of graph minors. We shall discuss pivot-minors and two recent results for proper pivot-minor-closed classes of graphs. In particular, that for

### Hyunwoo Lee (이현우), On perfect subdivision tilings

Room B332 IBS (기초과학연구원)

For a given graph $H$, we say that a graph $G$ has a perfect $H$-subdivision tiling if $G$ contains a collection of vertex-disjoint subdivisions of $H$ covering all vertices of

## May 2023

### Rob Morris, An exponential improvement for diagonal Ramsey

Room B332 IBS (기초과학연구원)

The Ramsey number $R(k)$ is the minimum n such that every red-blue colouring of the edges of the complete graph on n vertices contains a monochromatic copy of $K_k$. It

기초과학연구원 수리및계산과학연구단 이산수학그룹
대전 유성구 엑스포로 55 (우) 34126
IBS Discrete Mathematics Group (DIMAG)
Institute for Basic Science (IBS)
55 Expo-ro Yuseong-gu Daejeon 34126 South Korea
E-mail: dimag@ibs.re.kr, Fax: +82-42-878-9209