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Displaying similar documents to “On the polynomial expressions for the number of ways of coloring a map”

A decomposition of gallai multigraphs

Alexander Halperin, Colton Magnant, Kyle Pula (2014)

Discussiones Mathematicae Graph Theory

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An edge-colored cycle is rainbow if its edges are colored with distinct colors. A Gallai (multi)graph is a simple, complete, edge-colored (multi)graph lacking rainbow triangles. As has been previously shown for Gallai graphs, we show that Gallai multigraphs admit a simple iterative construction. We then use this structure to prove Ramsey-type results within Gallai colorings. Moreover, we show that Gallai multigraphs give rise to a surprising and highly structured decomposition into directed...

On rainbow connection.

Caro, Yair, Lev, Arie, Roditty, Yehuda, Tuza, Zsolt, Yuster, Raphael (2008)

The Electronic Journal of Combinatorics [electronic only]

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Rainbow Connection Number of Dense Graphs

Xueliang Li, Mengmeng Liu, Ingo Schiermeyer (2013)

Discussiones Mathematicae Graph Theory

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An edge-colored graph G is rainbow connected, if any two vertices are connected by a path whose edges have distinct colors. The rainbow connection number of a connected graph G, denoted rc(G), is the smallest number of colors that are needed in order to make G rainbow connected. In this paper we show that rc(G) ≤ 3 if |E(G)| ≥ [...] + 2, and rc(G) ≤ 4 if |E(G)| ≥ [...] + 3. These bounds are sharp.

Vertex rainbow colorings of graphs

Futaba Fujie-Okamoto, Kyle Kolasinski, Jianwei Lin, Ping Zhang (2012)

Discussiones Mathematicae Graph Theory

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In a properly vertex-colored graph G, a path P is a rainbow path if no two vertices of P have the same color, except possibly the two end-vertices of P. If every two vertices of G are connected by a rainbow path, then G is vertex rainbow-connected. A proper vertex coloring of a connected graph G that results in a vertex rainbow-connected graph is a vertex rainbow coloring of G. The minimum number of colors needed in a vertex rainbow coloring of G is the vertex rainbow connection number...

On the Rainbow Vertex-Connection

Xueliang Li, Yongtang Shi (2013)

Discussiones Mathematicae Graph Theory

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A vertex-colored graph is rainbow vertex-connected if any two vertices are connected by a path whose internal vertices have distinct colors. The rainbow vertex-connection of a connected graph G, denoted by rvc(G), is the smallest number of colors that are needed in order to make G rainbow vertexconnected. It was proved that if G is a graph of order n with minimum degree δ, then rvc(G) < 11n/δ. In this paper, we show that rvc(G) ≤ 3n/(δ+1)+5 for [xxx] and n ≥ 290, while rvc(G) ≤ 4n/(δ...