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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

The classical theorem of Vizing states that every graph of maximum degree $d$ admits an edge-coloring with at most $d+1$ colors. Furthermore, as it was earlier shown by K\H{o}nig, $d$ colors suffice if the graph is bipartite. We investigate…

Combinatorics · Mathematics 2016-08-23 Endre Csóka , Gabor Lippner , Oleg Pikhurko

We show that every 2-degenerate graph with maximum degree $\Delta$ has a strong edge-coloring with at most $8\Delta-4$ colors.

Combinatorics · Mathematics 2024-03-28 Rong Luo , Gexin Yu

A {\em strong edge coloring} of a graph $G$ is a proper edge coloring in which every color class is an induced matching. The {\em strong chromatic index} $\chiup_{s}'(G)$ of a graph $G$ is the minimum number of colors in a strong edge…

Combinatorics · Mathematics 2022-06-13 Tao Wang

We prove that in any strongly fan-planar drawing of a graph G the edges can be colored with at most three colors, such that no two edges of the same color cross. This implies that the thickness of strongly fan-planar graphs is at most…

Combinatorics · Mathematics 2022-08-29 Otfried Cheong , Maximilian Pfister , Lena Schlipf

A proper edge colouring of a graph is adjacent vertex distinguishing if no two adjacent vertices see the same set of colours. Using a clever application of the Local Lemma, Hatami (2005) proved that every graph with maximum degree $\Delta$…

Combinatorics · Mathematics 2020-11-04 Gwenaël Joret , William Lochet

A {\it proper conflict-free $c$-coloring} of a graph is a proper $c$-coloring such that each non-isolated vertex has a color appearing exactly once on its neighborhood. This notion was formally introduced by Fabrici et al., who proved that…

Combinatorics · Mathematics 2022-04-13 Eun-Kyung Cho , Ilkyoo Choi , Hyemin Kwon , Boram Park

An $acyclic$ edge coloring of a graph is a proper edge coloring such that there are no bichromatic cycles. The \emph{acyclic chromatic index} of a graph is the minimum number k such that there is an acyclic edge coloring using k colors and…

Discrete Mathematics · Computer Science 2009-08-18 Manu Basavaraju , L. Sunil Chandran

It is shown that any graph with maximum degree $\Delta$ in which the average degree of the induced subgraph on the set of all neighbors of any vertex exceeds $\frac{6k^2}{6k^2 + 1}\Delta + k + 6$ is either $(\Delta - k)$-colorable or…

Combinatorics · Mathematics 2012-10-02 Landon Rabern

An \emph{equitable coloring} of a graph is a proper vertex coloring such that the sizes of every two color classes differ by at most 1. Chen, Lih, and Wu conjectured that every connected graph $G$ with maximum degree $\Delta \geq 2$ has an…

Combinatorics · Mathematics 2012-03-05 Keaitsuda Nakprasit , Kittikorn Nakprasit

A graph $G$ is class II, if its chromatic index is at least $\Delta+1$. Let $H$ be a maximum $\Delta$-edge-colorable subgraph of $G$. The paper proves best possible lower bounds for $\frac{|E(H)|}{|E(G)|}$, and structural properties of…

Discrete Mathematics · Computer Science 2012-10-26 Vahan V. Mkrtchyan , Eckhard Steffen

A graph is said to be interval colourable if it admits a proper edge-colouring using palette $\mathbb{N}$ in which the set of colours incident to each vertex is an interval. The interval colouring thickness of a graph $G$ is the minimum $k$…

It was conjectured by the third author in about 1973 that every $d$-regular planar graph (possibly with parallel edges) can be $d$-edge-coloured, provided that for every odd set $X$ of vertices, there are at least $d$ edges between $X$ and…

Discrete Mathematics · Computer Science 2012-09-07 Maria Chudnovsky , Katherine Edwards , Paul Seymour

An acyclic edge coloring of a graph $G$ is a proper edge coloring such that every cycle is colored with at least three colors. The acyclic chromatic index $\chiup_{a}'(G)$ of a graph $G$ is the least number of colors in an acyclic edge…

Combinatorics · Mathematics 2018-02-20 Tao Wang , Yaqiong Zhang

The \textit{square} of a graph $G$, denoted by $G^2$, is obtained from $G$ by adding an edge to connect every pair of vertices with a common neighbor in $G$. In this paper we prove that for every planar graph $G$ with maximum degree at most…

Combinatorics · Mathematics 2023-08-15 Jiani Zou , Miaomiao Han , Hong-Jian Lai

A graph is $k$-planar if it can be drawn in the plane so that each edge is crossed at most $k$ times. Typically, the class of 1-planar graphs is among the most investigated graph families within the so-called "beyond planar graphs". A…

Combinatorics · Mathematics 2021-01-29 Xin Zhang , Yan Li

A proper conflict-free colouring of a graph is a colouring of the vertices such that any two adjacent vertices receive different colours, and for every non-isolated vertex $v$, some colour appears exactly once on the neighbourhood of $v$.…

Combinatorics · Mathematics 2025-05-01 Chun-Hung Liu , Bruce Reed

For planar graphs, we consider the problems of \emph{list edge coloring} and \emph{list total coloring}. Edge coloring is the problem of coloring the edges while ensuring that two edges that are adjacent receive different colors. Total…

Discrete Mathematics · Computer Science 2014-05-15 Marthe Bonamy , Benjamin Lévêque , Alexandre Pinlou

The chromatic index $\chi'(G)$ of a graph $G$ is the smallest $k$ for which $G$ admits an edge $k$-coloring such that any two adjacent edges have distinct colors. The strong chromatic index $\chi'_s(G)$ of $G$ is the smallest $k$ such that…

Combinatorics · Mathematics 2025-01-22 Yiqiao Wang , Ning Song , Jianfeng Wang , Weifan Wang

An edge-weighting of a graph is called vertex-coloring if the weighted degrees yield a proper vertex coloring of the graph. It is conjectured that for every graph without isolated edge, a vertex-coloring edge-weighting with the set {1,2,3}…

Combinatorics · Mathematics 2023-05-04 Ralph Keusch