We discuss relationships among T-colorings of graphs and chromatic numbers, fractional chromatic numbers, and circular chromatic numbers of distance graphs. We first prove that for any finite integral set T that contains 0, the asymptotic T-coloring ratio R(T ) is equal to the fractional chromatic n
Average distance in colored graphs
β Scribed by Peter Dankelmann; Wayne Goddard; Peter Slater
- Publisher
- John Wiley and Sons
- Year
- 2001
- Tongue
- English
- Weight
- 143 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0364-9024
- DOI
- 10.1002/jgt.1020
No coin nor oath required. For personal study only.
β¦ Synopsis
Abstract
For a graph G where the vertices are colored, the colored distance of G is defined as the sum of the distances between all unordered pairs of vertices having different colors. Then for a fixed supply s of colors, d~s~(G) is defined as the minimum colored distance over all colorings with s. This generalizes the concepts of median and average distance. In this paper we explore bounds on this parameter, especially a natural lower bound and the particular case of balanced 2βcolorings (equal numbers of red and blue). We show that the general problem is NPβhard but there is a polynomialβtime algorithm for trees. Β© 2001 John Wiley & Sons, Inc. J Graph Theory 38: 1β17, 2001
π SIMILAR VOLUMES
We present algorithms for minimum G -coloring k-colorable graphs drawn from random and semi-random models. In both models, an adversary initially splits Ε½ . the vertices into k color classes V , . . . , V of sizes β n each. In the first model,
The average distance p(G) of a graph G is the average among the distances between all pairs of vertices in G. For n 2 2, the average Steiner n-distance ,4G) of a connected graph G is the average Steiner distance over all sets of n vertices in G. It is shown that for a connected weighted graph G, pu,
Suppose D is a subset of Z. The distance graph G(Z, D) with distance set D is the graph with vertex set Z and two vertices x, y are adjacent if |x& y| # D. We introduce a coloring method for distance graphs, the pattern periodic coloring, and we shall compare this method with other general coloring
It is shown that, for β ) 0 and n ) n β , any complete graph K on n vertices 0 ' Ε½ . whose edges are colored so that no vertex is incident with more than 1 y 1r 2 y β n edges of the same color contains a Hamilton cycle in which adjacent edges have distinct colors. Moreover, for every k between 3 and