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We give an algorithm which for an input planar graph $G$ of $n$ vertices and integer $k$, in $\min\{O(n\log^3n),O(nk^2)\}$ time either constructs a branch-decomposition of $G$ with width at most $(2+\delta)k$, $\delta>0$ is a constant, or a…

数据结构与算法 · 计算机科学 2016-08-23 Qian-Ping Gu , Gengchun Xu

We show that for every integer $n\geq 1$ there exists a graph $G_n$ with $(1+o(1))n$ vertices and $n^{1 + o(1)}$ edges such that every $n$-vertex planar graph is isomorphic to a subgraph of $G_n$. The best previous bound on the number of…

组合数学 · 数学 2023-10-09 Louis Esperet , Gwenaël Joret , Pat Morin

The blow-up lemma states that a system of super-regular pairs contains all bounded degree spanning graphs as subgraphs that embed into a corresponding system of complete pairs. This lemma has far-reaching applications in extremal…

组合数学 · 数学 2025-08-29 Peter Allen , Julia Böttcher , Hiep Hàn , Yoshiharu Kohayakawa , Yury Person

We prove that every graph $G$ on $n$ vertices with no isolated vertices contains an induced subgraph of size at least $n/10000$ with all degrees odd. This solves an old and well-known conjecture in graph theory.

组合数学 · 数学 2021-04-02 Asaf Ferber , Michael Krivelevich

We discuss the problem of embedding graphs in the plane with restrictions on the vertex mapping. In particular, we introduce a technique for drawing planar graphs with a fixed vertex mapping that bounds the number of times edges bend. An…

计算几何 · 计算机科学 2012-06-05 Taylor Gordon

Given a function $g=g(n)$ we let ${\mathcal E}^g$ be the class of all graphs $G$ such that if $G$ has order $n$ (that is, has $n$ vertices) then it is embeddable in some surface of Euler genus at most $g(n)$, and let ${\widetilde{\mathcal…

组合数学 · 数学 2021-08-11 Colin McDiarmid , Sophia Saller

We show that every $n$-vertex planar graph admits a simultaneous embedding with no mapping and with fixed edges with any $(n/2)$-vertex planar graph. In order to achieve this result, we prove that every $n$-vertex plane graph has an induced…

数据结构与算法 · 计算机科学 2013-09-19 Patrizio Angelini , William Evans , Fabrizio Frati , Joachim Gudmundsson

A set $\mathcal{G}$ of planar graphs on the same number $n$ of vertices is called simultaneously embeddable if there exists a set $P$ of $n$ points in the plane such that every graph $G \in \mathcal{G}$ admits a (crossing-free)…

组合数学 · 数学 2023-09-14 Raphael Steiner

Given a class of graphs F, we say that a graph G is universal for F, or F-universal, if every H in F is contained in G as a subgraph. The construction of sparse universal graphs for various families F has received a considerable amount of…

组合数学 · 数学 2011-08-24 Daniel Johannsen , Michael Krivelevich , Wojciech Samotij

The vertex connectivity of a graph $G$ is the size of the smallest set of vertices $S$ such that $G \setminus S$ is disconnected. For the class of planar graphs, the problem of vertex connectivity is well-studied, both from structural and…

计算几何 · 计算机科学 2025-06-03 Therese Biedl , Karthik Murali

In this paper we study the fundamental problem of finding small dense subgraphs in a given graph. For a real number $s>2$, we prove that every graph on $n$ vertices with average degree at least $d$ contains a subgraph of average degree at…

组合数学 · 数学 2022-07-11 Oliver Janzer , Benny Sudakov , István Tomon

We provide a degree condition on a regular $n$-vertex graph $G$ which ensures the existence of a near optimal packing of any family $\mathcal H$ of bounded degree $n$-vertex $k$-chromatic separable graphs into $G$. In general, this degree…

组合数学 · 数学 2018-11-12 Padraig Condon , Jaehoon Kim , Daniela Kühn , Deryk Osthus

A seminal result of Lee asserts that the Ramsey number of any bipartite $d$-degenerate graph $H$ satisfies $\log r(H) = \log n + O(d)$. In particular, this bound applies to every bipartite graph of maximal degree $\Delta$. It remains a…

组合数学 · 数学 2024-10-28 Dylan J. Altschuler , Han Huang , Konstantin Tikhomirov

Motivated by applications in graph drawing and information visualization, we examine the planar split thickness of a graph, that is, the smallest $k$ such that the graph is $k$-splittable into a planar graph. A $k$-split operation…

In this paper we present an O(n log n) algorithm for finding a maximum flow in a directed planar graph, where the vertices are subject to capacity constraints, in addition to the arcs. If the source and the sink are on the same face, then…

离散数学 · 计算机科学 2009-05-05 Haim Kaplan , Yahav Nussbaum

The Planar Graph Product Structure Theorem of Dujmovi\'c et al. [J. ACM '20] says that every planar graph $G$ is contained in $H\boxtimes P\boxtimes K_3$ for some planar graph $H$ with treewidth at most 3 and some path $P$. This result has…

组合数学 · 数学 2025-02-05 Kevin Hendrey , David R. Wood

We study cross-graph charging schemes for graphs drawn in the plane. These are charging schemes where charge is moved across vertices of different graphs. Such methods have been recently applied to obtain various properties of…

计算几何 · 计算机科学 2012-09-04 Micha Sharir , Adam Sheffer

A separating path system for a graph $G$ is a collection $\mathcal{P}$ of paths in $G$ such that for every two edges $e$ and $f$ in $G$, there is a path in $\mathcal{P}$ that contains $e$ but not $f$. We show that every $n$-vertex graph has…

组合数学 · 数学 2024-05-30 Shoham Letzter

We show that if a graph G of order n contains many copies of a given subgraph H, then it contains a blow-up of H of order log n.

组合数学 · 数学 2007-11-26 Vladimir Nikiforov

We introduce and study the problem of constructing geometric graphs that have few vertices and edges and that are universal for planar graphs or for some sub-class of planar graphs; a geometric graph is \emph{universal} for a class…

组合数学 · 数学 2020-06-22 Fabrizio Frati , Michael Hoffmann , Csaba D. Tóth