Set vertex colorings and joins of graphs

Futaba Okamoto; Craig W. Rasmussen; Ping Zhang

Displaying similar documents to “Set vertex colorings and joins of graphs”

Radio antipodal colorings of graphs

Gary Chartrand, David Erwin, Ping Zhang (2002)

Mathematica Bohemica

Similarity:

A radio antipodal coloring of a connected graph $G$ with diameter $d$ is an assignment of positive integers to the vertices of $G$ , with $x \in V (G)$ assigned $c (x)$ , such that $d (u, v) + | c (u) - c (v) | \geq d$ for every two distinct vertices $u$ , $v$ of $G$ , where $d (u, v)$ is the distance between $u$ and $v$ in $G$ . The radio antipodal coloring number $a c (c)$ of a radio antipodal coloring $c$ of $G$ is the maximum color assigned to a vertex of $G$ . The radio antipodal chromatic number $a c (G)$ of $G$ is $min {a c (c)}$ over all radio antipodal colorings $c$ of $G$ . Radio antipodal chromatic numbers...

Defining sets in (proper) vertex colorings of the Cartesian product of a cycle with a complete graph

D. Ali Mojdeh (2006)

Discussiones Mathematicae Graph Theory

Similarity:

In a given graph G = (V,E), a set of vertices S with an assignment of colors to them is said to be a defining set of the vertex coloring of G, if there exists a unique extension of the colors of S to a c ≥ χ(G) coloring of the vertices of G. A defining set with minimum cardinality is called a minimum defining set and its cardinality is the defining number, denoted by d(G,c). The d(G = Cₘ × Kₙ, χ(G)) has been studied. In this note we show that the exact value of defining number d(G =...

On detectable colorings of graphs

Henry Escuadro, Ping Zhang (2005)

Mathematica Bohemica

Similarity:

Let $G$ be a connected graph of order $n \geq 3$ and let $c E (G) \to {1, 2, ..., k}$ be a coloring of the edges of $G$ (where adjacent edges may be colored the same). For each vertex $v$ of $G$ , the color code of $v$ with respect to $c$ is the $k$ -tuple $c (v) = (a_{1}, a_{2}, \dots, a_{k})$ , where $a_{i}$ is the number of edges incident with $v$ that are colored $i$ ( $1 \leq i \leq k$ ). The coloring $c$ is detectable if distinct vertices have distinct color codes. The detection number $det (G)$ of $G$ is the minimum positive integer $k$ for which $G$ has a detectable $k$ -coloring. We establish a formula for the...

On the dominator colorings in trees

Houcine Boumediene Merouane, Mustapha Chellali (2012)

Discussiones Mathematicae Graph Theory

Similarity:

In a graph G, a vertex is said to dominate itself and all its neighbors. A dominating set of a graph G is a subset of vertices that dominates every vertex of G. The domination number γ(G) is the minimum cardinality of a dominating set of G. A proper coloring of a graph G is a function from the set of vertices of the graph to a set of colors such that any two adjacent vertices have different colors. A dominator coloring of a graph G is a proper coloring such that every vertex of V dominates...

On stratification and domination in graphs

Ralucca Gera, Ping Zhang (2006)

Discussiones Mathematicae Graph Theory

Similarity:

A graph G is 2-stratified if its vertex set is partitioned into two classes (each of which is a stratum or a color class), where the vertices in one class are colored red and those in the other class are colored blue. Let F be a 2-stratified graph rooted at some blue vertex v. An F-coloring of a graph is a red-blue coloring of the vertices of G in which every blue vertex v belongs to a copy of F rooted at v. The F-domination number $γ_{F} (G)$ is the minimum number of red vertices in an F-coloring...

Set colorings in perfect graphs

Ralucca Gera, Futaba Okamoto, Craig Rasmussen, Ping Zhang (2011)

Mathematica Bohemica

Similarity:

For a nontrivial connected graph $G$ , let $c : V (G) \to ℕ$ be a vertex coloring of $G$ where adjacent vertices may be colored the same. For a vertex $v \in V (G)$ , the neighborhood color set $NC (v)$ is the set of colors of the neighbors of $v$ . The coloring $c$ is called a set coloring if $NC (u) \neq NC (v)$ for every pair $u, v$ of adjacent vertices of $G$ . The minimum number of colors required of such a coloring is called the set chromatic number $χ_{s} (G)$ . We show that the decision variant of determining $χ_{s} (G)$ is NP-complete in the general case, and show that...

3-consecutive c-colorings of graphs

Csilla Bujtás, E. Sampathkumar, Zsolt Tuza, M.S. Subramanya, Charles Dominic (2010)

Discussiones Mathematicae Graph Theory

Similarity:

A 3-consecutive C-coloring of a graph G = (V,E) is a mapping φ:V → ℕ such that every path on three vertices has at most two colors. We prove general estimates on the maximum number ${(χ ̅)}_{3 C C} (G)$ of colors in a 3-consecutive C-coloring of G, and characterize the structure of connected graphs with ${(χ ̅)}_{3 C C} (G) \geq k$ for k = 3 and k = 4.

A new upper bound for the chromatic number of a graph

Ingo Schiermeyer (2007)

Discussiones Mathematicae Graph Theory

Similarity:

Let G be a graph of order n with clique number ω(G), chromatic number χ(G) and independence number α(G). We show that χ(G) ≤ [(n+ω+1-α)/2]. Moreover, χ(G) ≤ [(n+ω-α)/2], if either ω + α = n + 1 and G is not a split graph or α + ω = n - 1 and G contains no induced $K_{ω + 3} - C ₅$ .

Multicolor Ramsey numbers for paths and cycles

Tomasz Dzido (2005)

Discussiones Mathematicae Graph Theory

Similarity:

For given graphs G₁,G₂,...,Gₖ, k ≥ 2, the multicolor Ramsey number R(G₁,G₂,...,Gₖ) is the smallest integer n such that if we arbitrarily color the edges of the complete graph on n vertices with k colors, then it is always a monochromatic copy of some $G_{i}$ , for 1 ≤ i ≤ k. We give a lower bound for k-color Ramsey number R(Cₘ,Cₘ,...,Cₘ), where m ≥ 8 is even and Cₘ is the cycle on m vertices. In addition, we provide exact values for Ramsey numbers R(P₃,Cₘ,Cₚ), where P₃ is the path on 3 vertices,...