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 of $\text{ex}_{\hom}(n,X)$ have recently been determined for all surfaces $X$. I will discuss these results, as well as ongoing work bounding $\text{ex}_{\hom}(n,X)$ for arbitrary 2-dimensional

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 a set $\mathcal P$ of $k$ pairwise vertex-disjoint paths connecting $s_i$ and $t_i$ for all indices $i\in\{1,\ldots,k\}$. This problem has been studied extensively due to

Marcelo Sales, On Pisier type problems

Zoom ID: 224 221 2686 (ibsecopro)

A subset $A\subseteq \mathbb Z$ of integers is free if for every two distinct subsets $B, B'\subseteq A$ we have \Pisier asked if for every subset $A\subseteq \mathbb Z$ of integers the following two statement are equivalent: (i) $A$ is a union of finitely many free sets. (ii) There exists $\epsilon>0$ such that every finite

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 theory; when a family F is union-closed (the union of sets of F is itself a set of $\mathcal F$), then $\mathcal F$ contains an

Paul Seymour, A loglog step towards the Erdős-Hajnal conjecture

Zoom ID: 869 4632 6610 (ibsdimag)

In 1977, Erdős and Hajnal made the conjecture that, for every graph $H$, there exists $c>0$ such that every $H$-free graph $G$ has a clique or stable set of size at least $|G|^c$; and they proved that this is true with $|G|^c$ replaced by $2^{c\sqrt{\log |G|}}$. There has no improvement on this result (for general

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 also introduce recent extremal problems.

Qizhong Lin, Two classical Ramsey-Turán numbers involving triangles

Zoom ID: 224 221 2686 (ibsecopro)

In 1993, Erdős, Hajnal, Simonovits, Sós and Szemerédi proposed to determine the value of Ramsey-Turán density $\rho(3,q)$ for $q\ge3$. Erdős et al. (1993) and Kim, Kim and Liu (2019) proposed two corresponding conjectures. However, we only know four values of this Ramsey-Turán density by Erdős et al. (1993). There is no progress on this classical

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 k, but any proper subgraph has a chromatic number less than k. The problem remains open for any integer k ≥ 4. Our presentation will

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 talk about a construction that shows that their structure might be more complicated than people conjectured.

Jie Han, Spanning trees in expanders

Zoom ID: 224 221 2686 (ibsecopro)

We consider the spanning tree embedding problem in dense graphs without bipartite holes and sparse graphs. In 2005, Alon, Krivelevich and Sudakov asked for determining the best possible spectral gap forcing an $(n,d,\lambda)$-graph to be $T(n, \Delta)$-universal. In this talk, we introduce our recent work on this conjecture.

IBS 이산수학그룹 Discrete Mathematics Group
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:, Fax: +82-42-878-9209
Copyright © IBS 2018. All rights reserved.