Ping Wang, Jian-Liang Wu (2004)
Discussiones Mathematicae Graph Theory
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Let G be a 2-connected planar graph with maximum degree Δ such that G has no cycle of length from 4 to k, where k ≥ 4. Then the total chromatic number of G is Δ +1 if (Δ,k) ∈ {(7,4),(6,5),(5,7),(4,14)}.
Hanna Furmánczyk, Marek Kubale, Vahan V. Mkrtchyan (2017)
Discussiones Mathematicae Graph Theory
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A graph is equitably k-colorable if its vertices can be partitioned into k independent sets in such a way that the numbers of vertices in any two sets differ by at most one. The smallest k for which such a coloring exists is known as the equitable chromatic number of G and denoted by 𝜒=(G). It is known that the problem of computation of 𝜒=(G) is NP-hard in general and remains so for corona graphs. In this paper we consider the same model of coloring in the case of corona multiproducts...
Jaroslav Nešetřil (1973)
Časopis pro pěstování matematiky
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J. Czap, S. Jendrol’, J. Valiska (2017)
Discussiones Mathematicae Graph Theory
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Given three planar graphs F,H, and G, an (F,H)-WORM coloring of G is a vertex coloring such that no subgraph isomorphic to F is rainbow and no subgraph isomorphic to H is monochromatic. If G has at least one (F,H)-WORM coloring, then W−F,H(G) denotes the minimum number of colors in an (F,H)-WORM coloring of G. We show that (a) W−F,H(G) ≤ 2 if |V (F)| ≥ 3 and H contains a cycle, (b) W−F,H(G) ≤ 3 if |V (F)| ≥ 4 and H is a forest with Δ (H) ≥ 3, (c) W−F,H(G) ≤ 4 if |V (F)| ≥ 5 and H is...
Robert Fidytek, Hanna Furmańczyk, Paweł Żyliński (2009)
Discussiones Mathematicae Graph Theory
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The Kneser graph K(n,k) is the graph whose vertices correspond to k-element subsets of set {1,2,...,n} and two vertices are adjacent if and only if they represent disjoint subsets. In this paper we study the problem of equitable coloring of Kneser graphs, namely, we establish the equitable chromatic number for graphs K(n,2) and K(n,3). In addition, for sufficiently large n, a tight upper bound on equitable chromatic number of graph K(n,k) is given. Finally, the cases of K(2k,k) and K(2k+1,k)...
Janez Žerovnik (2006)
Mathematica Slovaca
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Sakib A. Mondal (2011)
Discussiones Mathematicae Graph Theory
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In this paper we prove that every planar graph without 4, 5 and 8-cycles is 3-colorable.
William F. Klostermeyer, Gary MacGillivray (2004)
Discussiones Mathematicae Graph Theory
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We examine subgraphs of oriented graphs in the context of oriented coloring that are analogous to cliques in traditional vertex coloring. Bounds on the sizes of these subgraphs are given for planar, outerplanar, and series-parallel graphs. In particular, the main result of the paper is that a planar graph cannot contain an induced subgraph D with more than 36 vertices such that each pair of vertices in D are joined by a directed path of length at most two.
Hajiabolhassan, Hossein, Taherkhani, Ali (2010)
The Electronic Journal of Combinatorics [electronic only]
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Norine, Serguei, Zhu, Xuding (2008)
The Electronic Journal of Combinatorics [electronic only]
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Andrey A. Dobrynin, Leonid S. Mel'nikov (2012)
Discussiones Mathematicae Graph Theory
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Let G be a simple 4-regular plane graph and let S be a decomposition of G into edge-disjoint cycles. Suppose that every two adjacent edges on a face belong to different cycles of S. Such a graph G arises as a superposition of simple closed curves in the plane with tangencies disallowed. Studies of coloring of graphs of this kind were originated by Grötzsch. Two 4-chromatic graphs generated by circles in the plane were constructed by Koester in 1984 [10,11,12]. Until now, no other examples...
Erdős, Paul (1995)
Publications de l'Institut Mathématique. Nouvelle Série
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Csilla Bujtás, Zsolt Tuza (2016)
Discussiones Mathematicae Graph Theory
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A K3-WORM coloring of a graph G is an assignment of colors to the vertices in such a way that the vertices of each K3-subgraph of G get precisely two colors. We study graphs G which admit at least one such coloring. We disprove a conjecture of Goddard et al. [Congr. Numer. 219 (2014) 161-173] by proving that for every integer k ≥ 3 there exists a K3-WORM-colorable graph in which the minimum number of colors is exactly k. There also exist K3-WORM colorable graphs which have a K3-WORM...
Ingo Schiermeyer (2005)
Discussiones Mathematicae Graph Theory
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The cycle-complete graph Ramsey number r(Cₘ,Kₙ) is the smallest integer N such that every graph G of order N contains a cycle Cₘ on m vertices or has independence number α(G) ≥ n. It has been conjectured by Erdős, Faudree, Rousseau and Schelp that r(Cₘ,Kₙ) = (m-1)(n-1)+1 for all m ≥ n ≥ 3 (except r(C₃,K₃) = 6). This conjecture holds for 3 ≤ n ≤ 6. In this paper we will present a proof for r(C₅,K₇) = 25.