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We introduce a method to embed edge-colored graphs into families of expander graphs, which generalizes a framework developed by Dragani\'c, Krivelevich, and Nenadov (2022). As an application, we show that each family of sufficiently…

Combinatorics · Mathematics 2025-01-27 Ben Lund , Chuandong Xu

We show that a cubic graph $G$ of order $n$ has an induced $2$-regular subgraph of order at least a) $\frac{n-2}{4-\frac{4}{k}}$, if $G$ has no induced cycle of length more than $k$, b) $\frac{5n+6}{8}$, if $G$ has no induced cycle of…

Combinatorics · Mathematics 2014-06-11 Michael A. Henning , Felix Joos , Christian Löwenstein , Dieter Rautenbach

This exposition contains a short and streamlined proof of the recent result of Kwan, Letzter, Sudakov and Tran that every triangle-free graph with minimum degree $d$ contains an induced bipartite subgraph with average degree $\Omega(\ln…

Combinatorics · Mathematics 2020-06-11 Stefan Glock

An induced path factor of a graph $G$ is a set of induced paths in $G$ with the property that every vertex of $G$ is in exactly one of the paths. The induced path number $\rho(G)$ of $G$ is the minimum number of paths in an induced path…

Combinatorics · Mathematics 2021-04-19 Saieed Akbari , Daniel Horsley , Ian M. Wanless

A connected matching in a graph G consists of a set of pairwise disjoint edges whose covered vertices induce a connected subgraph of G. While finding a connected matching of maximum cardinality is a well-solved problem, it is NP-hard to…

Discrete Mathematics · Computer Science 2024-08-12 Phillippe Samer , Phablo F. S. Moura

We show that every cubic bridgeless graph with n vertices has at least 3n/4-10 perfect matchings. This is the first bound that differs by more than a constant from the maximal dimension of the perfect matching polytope.

Combinatorics · Mathematics 2015-09-28 Louis Esperet , Daniel Kral , Petr Skoda , Riste Skrekovski

Mader [J. Combin. Theory Ser. B 40 (1986) 152-158] proved that every $k$-edge-connected graph $G$ with minimum degree at least $k+1$ contains a vertex $u$ such that $G-\{u\}$ is still $k$-edge-connected. In this paper, we prove that every…

Combinatorics · Mathematics 2023-12-12 Qing Yang , Yingzhi Tian

A conjecture of Fan and Raspaud [3] asserts that every bridgeless cubic graph con-tains three perfect matchings with empty intersection. Kaiser and Raspaud [6] sug-gested a possible approach to this problem based on the concept of a…

Discrete Mathematics · Computer Science 2008-09-30 Jean-Luc Fouquet , Jean-Marie Vanherpe

A conjecture due to the fourth author states that every $d$-regular planar multigraph can be $d$-edge-coloured, provided that for every odd set $X$ of vertices, there are at least $d$ edges between $X$ and its complement. For $d = 3$ this…

Discrete Mathematics · Computer Science 2012-10-30 Maria Chudnovsky , Katherine Edwards , Ken-ichi Kawarabayashi , Paul Seymour

In this article we present theoretical and computational results on the existence of polyhedral embeddings of graphs. The emphasis is on cubic graphs. We also describe an efficient algorithm to compute all polyhedral embeddings of a given…

Combinatorics · Mathematics 2023-06-22 Gunnar Brinkmann , Thomas Tucker , Nico Van Cleemput

A matchstick graph is a plane graph with edges drawn as unit-distance line segments. Harborth introduced these graphs in 1981 and conjectured that the maximum number of edges for a matchstick graph on $n$ vertices is $\lfloor…

Combinatorics · Mathematics 2023-06-16 Jérémy Lavollée , Konrad Swanepoel

Archdeacon (1987) proved that graphs embeddable on a fixed surface can be $3$-coloured so that each colour class induces a subgraph of bounded maximum degree. Edwards, Kang, Kim, Oum and Seymour (2015) proved that graphs with no…

Combinatorics · Mathematics 2019-07-15 Patrice Ossona de Mendez , Sang-il Oum , David R. Wood

A matching of a graph is a set of edges without common end vertex. A graph is called 1-planar if it admits a drawing in the plane such that each edge is crossed at most once. Recently, Biedl and Wittnebel proved that every 1-planar graph…

Combinatorics · Mathematics 2022-07-11 Yuanqiu Huang , Zhangdong Ouyang , Fengming Dong

We prove that every bipartite graph of sufficiently large average degree has either a $K_{t,t}$-subgraph or an induced subgraph of average degree at least $t$ and girth at least $6$. We conjecture that "$6$" can be replaced by "$k$", which…

Combinatorics · Mathematics 2020-04-02 Rose McCarty

Strengthened notions of a matching $M$ of a graph $G$ have been considered, requiring that the matching $M$ has some properties with respect to the subgraph $G_M$ of $G$ induced by the vertices covered by $M$: If $M$ is the unique perfect…

Combinatorics · Mathematics 2025-09-16 Yuquan Lin , Wensong Lin

Let $G$ be a simple graph and $I(G)$ be its edge ideal. In this article, we study the Castelnuovo-Mumford regularity of symbolic powers of edge ideals of join of graphs. As a consequence, we prove Minh's conjecture for wheel graphs,…

Commutative Algebra · Mathematics 2020-08-04 Arvind Kumar , Rajiv Kumar , Rajib Sarkar

In this paper we study variations of an old result by M\"{u}ller, Reiterman, and the last author stating that a countable graph has a subgraph with infinite degrees if and only if in any labeling of the vertices (or edges) of this graph by…

Combinatorics · Mathematics 2019-05-10 Andrii Arman , Bradley Elliott , Vojtěch Rödl

In the last decade, algorithmic frameworks based on a structural graph parameter called mim-width have been developed to solve generally NP-hard problems. However, it is known that the frameworks cannot be applied to the Clique problem, and…

Data Structures and Algorithms · Computer Science 2024-05-27 Yota Otachi , Akira Suzuki , Yuma Tamura

We study the problem of finding homomorphisms into odd cycles from planar graphs with high odd-girth. The Jaeger-Zhang conjecture states that every planar graph of odd-girth at least $4k+1$ admits a homomorphism to the odd cycle $C_{2k+1}$.…

Combinatorics · Mathematics 2024-02-06 Daniel W. Cranston , Jiaao Li , Zhouningxin Wang , Chunyan Wei

A graph is $k$-degenerate if every subgraph has minimum degree at most $k$. We provide lower bounds on the size of a maximum induced 2-degenerate subgraph in a triangle-free planar graph. We denote the size of a maximum induced 2-degenerate…

Combinatorics · Mathematics 2018-02-21 Zdeněk Dvořák , Tom Kelly
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