기초과학연구원 이산수학그룹
An odd $$-factor of a graph is a spanning subgraph $H$ such that for every vertex $v \in V(G)$, $1 \le d_H(v) \le b$, and $d_H(v)$ is odd. For positive integers $r \ge 3$ and $b \le r$, Lu, Wu, and Yang gave an upper bound for the third largest eigenvalue in an $r$-regular graph with even number of …
We discuss how the model theoretic notion of first-order transduction allows to define a notion of structural sparsity, and give some example of applications, like existence of low shrub-depth decompositions for tranductions of bounded expansion classes, characterization of transductions of classes with bounded pathwidth, decompositions of graphs with bounded rank-width into cographs.
Given a finite set of elements $V$ and a family $\mathcal{C}$ of subsets of $V$, the set covering problem is to find a minimum cardinality subset of $V$ intersecting every subset in the family $\mathcal{C}$. The set covering problem, also known as the hitting set problem, admits a simple integer linear programming formulation. The constraint …
Schedule July 22 Monday 10:00-11:00 Introduction, 11:00-12:00 Open Problems July 23 Tuesday 10:00-10:30 Stefan Kratsch, Humboldt-Universität zu Berlin, Germany Elimination Distances, Blocking Sets, and Kernels for Vertex Cover 10:45-11:15 Benjamin Bergougnoux, University Clermont Auvergne, France More applications of the d-neighbor equivalence 11:30-12:00 Yixin Cao, Hong Kong Polytechnic University, China Enumerating Maximal Induced Subgraphs 13:30-14:30 Open Problems …
Invited Speakers Jaehoon Kim (김재훈), KAIST Hong Liu (刘鸿), University of Warwick Abhishek Methuku, IBS Discrete Mathematics Group Péter Pál Pach, Budapest University of Technology and Economics Schedule August 12, Monday 11:00am-12:00pm Jaehoon Kim (김재훈): Tree decompositions of graphs without large bipartite holes 12:00pm-1:30pm Lunch 1:30pm-2:30pm Abhishek Methuku: Bipartite Turán problems for ordered graphs 3:00pm-4:00pm Péter Pál …
The annual conference on Combinatorics Workshop (조합론 학술대회) began in 2004 by the Yonsei University BK21 Research Group. This year it will take place in Songdo, Incheon, August 13-15, 2019. Due to the capacity (50 persons) of the place, we are able to limit your registration. In principle, registration is on a first-come, first-served basis. …
In this talk we shall discuss how quickly the genus of the Erdős-Rényi random graph grows as the number of edges increases and how dramatically a small number of random edges can increase the genus of a randomly perturbed graph. (Joint work with Chris Dowden and Michael Krivelevich)
Given a graph $G$, we define $\textrm{ex}_c(G)$ to be the minimum value of $t$ for which there exists a constant $N(t,G)$ such that every $t$-connected graph with at least $N(t,G)$ vertices contains $G$ as a minor. The value of $\textrm{ex}_c(G)$ is known to be tied to the vertex cover number $\tau(G)$, and in fact $\tau(G)\leq …
Let $F$ and $H$ be graphs. The subgraph counting function $\operatorname{ex}(n,H,F)$ is defined as the maximum possible number of subgraphs $H$ in an $n$-vertex $F$-free graph. This function is a direct generalization of the Turán function as $\operatorname{ex}(n,F)=\operatorname{ex}(n,K_2,F)$. The systematic study of $\operatorname{ex}(n,H,F)$ was initiated by Alon and Shikhelman in 2016 who generalized several classical …
Given a graph $G$, there are several natural hypergraph families one can define. Among the least restrictive is the family $BG$ of so-called Berge copies of the graph $G$. In this talk, we discuss Turán problems for families $BG$ in $r$-uniform hypergraphs for various graphs $G$. In particular, we are interested in general results in …
