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For an oriented graph $G$, the least number of colours required to oriented colour $G$ is called the oriented chromatic number of $G$ and denoted $\chi_o(G)$.For a non-negative integer $g$ let $\chi_o(g)$ be the least integer such that…

Combinatorics · Mathematics 2024-09-23 Alexander Clow

We introduce a new tool useful for greedy coloring, which we call the forb-flex method, and apply it to odd coloring and proper conflict-free coloring of planar graphs. The odd chromatic number, denoted $\chi_{\mathsf{o}}(G)$, is the…

An edge-colored graph $G$ is $k$-color connected if, between each pair of vertices, there exists a path using at least $k$ different colors. The $k$-color connection number of $G$, denoted by $cc_{k}(G)$, is the minimum number of colors…

Combinatorics · Mathematics 2017-03-29 Hong Chang , Zhong Huang , Xueliang Li

A decomposition of a non-empty simple graph $G$ is a pair $[G,P]$, such that $P$ is a set of non-empty induced subgraphs of $G$, and every edge of $G$ belongs to exactly one subgraph in $P$. The chromatic index $\chi'([G,P])$ of a…

Combinatorics · Mathematics 2019-10-29 Clemens Huemer , Dolores Lara , Christian Rubio-Montiel

A domination coloring of a graph $G$ is a proper vertex coloring of $G$ such that each vertex of $G$ dominates at least one color class, and each color class is dominated by at least one vertex. The minimum number of colors among all…

Discrete Mathematics · Computer Science 2019-09-10 Yangyang Zhou , Dongyang Zhao

A total coloring of a graph $G$ is a coloring of the vertices and edges such that two adjacent or incident elements receive different colors. The minimum number of colors required for a total coloring of a graph $G$ is called the total…

Combinatorics · Mathematics 2025-09-05 Zakir Deniz , Hakan Guler

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 Jijuan Chen , Tao Wang , Huiqin Zhang

A graph/multigraph $G$ is locally irregular if endvertices of every its edge possess different degrees. The locally irregular edge coloring of $G$ is its edge coloring with the property that every color induces a locally irregular…

Combinatorics · Mathematics 2024-10-04 Igor Grzelec , Tomáš Madaras , Alfréd Onderko , Roman Soták

Let $f$ be a proper $k$-coloring of a connected graph $G$ and $\Pi=(V_1,V_2,...,V_k)$ be an ordered partition of $V(G)$ into the resulting color classes. For a vertex $v$ of $G$, the color code of $v$ with respect to $\Pi$ is defined to be…

Combinatorics · Mathematics 2012-01-24 Ali Behtoei

The Grundy number of a graph $G$ is the maximum number of colors used by the First-Fit coloring of $G$ and is denoted by $\Gamma(G)$. Similarly, the ${\rm b}$-chromatic number ${\rm{b}}(G)$ of $G$ expresses the worst case behavior of…

Combinatorics · Mathematics 2020-04-01 Manouchehr Zaker

The distinguishing number $D(G)$ of a graph $G$ is the least integer $d$ such that $G$ has a vertex labeling with $d$ labels that is preserved only by a trivial automorphism. The distinguishing chromatic number $\chi_{D}(G)$ of $G$ is…

Combinatorics · Mathematics 2017-09-29 Saeid Alikhani , Samaneh Soltani

Indicated coloring is a graph coloring game in which two players collectively color the vertices of a graph in the following way. In each round the first player (Ann) selects a vertex, and then the second player (Ben) colors it properly,…

Combinatorics · Mathematics 2020-02-07 P. Francis , S. Francis Raj , M. Gokulnath

An edge-coloured graph $G$ is called $properly$ $connected$ if every two vertices are connected by a proper path. The $proper$ $connection$ $number$ of a connected graph $G$, denoted by $pc(G)$, is the smallest number of colours that are…

Combinatorics · Mathematics 2018-06-26 Xiaxia Guan , Lina Xue , Eddie Cheng , Weihua Yang

We introduce a new concept in graph coloring motivated by the popular Sudoku puzzle. Let $G=(V,E)$ be a graph of order $n$ with chromatic number $\chi(G)=k$ and let $S\subseteq V.$ Let $\mathscr C_0$ be a $k$-coloring of the induced…

Combinatorics · Mathematics 2022-06-17 Gee-Choon Lau , J. Maria Jeyaseeli , Wai-Chee Shiu , S. Arumugam

We consider the $t$-improper chromatic number of the Erd{\H o}s-R{\'e}nyi random graph $G(n,p)$. The t-improper chromatic number $\chi^t(G)$ of $G$ is the smallest number of colours needed in a colouring of the vertices in which each colour…

Combinatorics · Mathematics 2010-09-08 Ross J. Kang , Colin McDiarmid

We introduce the notion of a properly ordered coloring (POC) of a weighted graph, that generalizes the notion of vertex coloring of a graph. Under a POC, if $xy$ is an edge, then the larger weighted vertex receives a larger color; in the…

Combinatorics · Mathematics 2021-02-18 Shinya Fujita , Sergey Kitaev , Shizuka Sato , Li-Da Tong

The chromatic number $\chi(G)$ of a graph $G$, that is, the smallest number of colors required to color the vertices of $G$ so that no two adjacent vertices are assigned the same color, is a classic and extensively studied parameter. Here…

Combinatorics · Mathematics 2021-04-23 Anders Martinsson , Konstantinos Panagiotou , Pascal Su , Miloš Trujić

Given a graph G, a colouring is an assignment of colours to the vertices of G so that no two adjacent vertices are coloured the same. If all colour classes have size at most t, then we call the colouring t-bounded, and the t-bounded…

Combinatorics · Mathematics 2024-09-27 Annika Heckel , Konstantinos Panagiotou

Given a graph $G$, a mutual-visibility coloring of $G$ is introduced as follows. We color two vertices $x,y\in V(G)$ with a same color, if there is a shortest $x,y$-path whose internal vertices have different colors than $x,y$. The smallest…

Combinatorics · Mathematics 2024-08-07 Sandi Klavžar , Dorota Kuziak , Juan Carlos Valenzuela Tripodoro , Ismael G. Yero

A vertex coloring of a given graph $G$ is conflict-free if the closed neighborhood of every vertex contains a unique color (i.e. a color appearing only once in the neighborhood). The minimum number of colors in such a coloring is the…

Combinatorics · Mathematics 2020-09-07 Michał Dębski , Jakub Przybyło
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