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Let over(G, →) be a directed graph. A transitive fraternal augmentation of over(G, →) is a directed graph over(H, →) with the same vertex set, including all the arcs of over(G, →) and such that for any vertices x, y, z, 1.if (x, y) ∈ E (over(G, →)) and (x, z) ∈ E (over(G, →)) then (y, z) ∈ E (over(H, →)) or (z, y) ∈ E (over(H, →)) (fraternity);2.if (x, y) ∈ E (over(G, →)) and (y, z) ∈ E (over(G, →)) then (x, z) ∈ E (over(H, →)) (transitivity). In this paper, we explore some generalization of the transitive fraternal augmentations for directed graphs and its applications. In particular, we show that the 2-coloring number col2 (G) ≤ O (∇1 (G) ∇0 (G)2), where ∇k (G) (k ≥ 0) denotes the greatest reduced average density with depth k of a graph G; we give a constructive proof that ∇k (G) bounds the distance (k + 1)-coloring number colk + 1 (G) with a function f (∇k (G)). On the other hand, ∇k (G) ≤ (col2 k + 1 (G))2 k + 1. We also show that an inductive generalization of transitive fraternal augmentations can be used to study nonrepetitive colorings of graphs. © 2009 Elsevier B.V. All rights reserved.
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Discrete Mathematics
ISSN: 0012-365X
Year: 2009
Issue: 13
Volume: 309
Page: 4614-4623
0 . 5 4 8
JCR@2009
0 . 7 0 0
JCR@2023
JCR Journal Grade:3
CAS Journal Grade:1
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