Results 231 to 240 of about 31,573 (274)
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Czechoslovak Mathematical Journal, 2002
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Chartrand, Gary, Zhang, Ping
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Chartrand, Gary, Zhang, Ping
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Star Extremal Circulant Graphs
SIAM Journal on Discrete Mathematics, 1999A graph is said to be star extremal if its fractional chromatic number is equal to its circular chromatic number. In this paper, it is proven that some families of circulant graphs are star extremal. The results generalize some earlier results obtained by \textit{A. F. Sidorenko} [Discrete Math.
Lih, Ko-Wei +2 more
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Extreme-Support Total Monophonic Graphs
Bulletin of the Iranian Mathematical Society, 2021zbMATH Open Web Interface contents unavailable due to conflicting licenses.
Kathiresan Ganesamoorthy +2 more
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Discrete Mathematics, Algorithms and Applications, 2012
For a connected graph G of order p ≥ 2 and a set W ⊆ V(G), a tree T contained in G is a Steiner tree with respect to W if T is a tree of minimum order with W ⊆ V(T). The set S(W) consists of all vertices in G that lie on some Steiner tree with respect to W. The set W is a Steiner set for G if S(W) = V(G).
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For a connected graph G of order p ≥ 2 and a set W ⊆ V(G), a tree T contained in G is a Steiner tree with respect to W if T is a tree of minimum order with W ⊆ V(T). The set S(W) consists of all vertices in G that lie on some Steiner tree with respect to W. The set W is a Steiner set for G if S(W) = V(G).
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Extremal Graphs for Homomorphisms II
Journal of Graph Theory, 2013AbstractExtremal problems for graph homomorphisms have recently become a topic of much research. Let denote the number of homomorphisms from G to H. A natural set of problems arises when we fix an image graph H and determine which graph(s) G on n vertices and m edges maximize .
Cutler, Jonathan, Radcliffe, A. J.
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Characterizations of Strength Extremal Graphs
Graphs and Combinatorics, 2013zbMATH Open Web Interface contents unavailable due to conflicting licenses.
Gu, Xiaofeng +3 more
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Extremal subgraphs of random graphs
Random Structures & Algorithms, 2012AbstractWe prove that there is a constant c > 0, such that whenever p ≥ n‐c, with probability tending to 1 when n goes to infinity, every maximum triangle‐free subgraph of the random graph Gn,p is bipartite. This answers a question of Babai, Simonovits and Spencer (Babai et al., J Graph Theory 14 (1990) 599–622).
Brightwell, G. +2 more
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2020
A graph is called singular if its adjacency matrix is singular. The problem of characterizing all singular graphs was posed in 1957 by L. Collatz and U. Sinogowitz. Since then, it has been studied intensely due to its great importance in mathematics and in chemistry.
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A graph is called singular if its adjacency matrix is singular. The problem of characterizing all singular graphs was posed in 1957 by L. Collatz and U. Sinogowitz. Since then, it has been studied intensely due to its great importance in mathematics and in chemistry.
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2005
In this chapter we study how global parameters of a graph, such as its edge density or chromatic number, can influence its local substructures. How many edges, for instance, do we have to give a graph on n vertices to be sure that, no matter how these edges are arranged, the graph will contain a K r subgraph for some given r?
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In this chapter we study how global parameters of a graph, such as its edge density or chromatic number, can influence its local substructures. How many edges, for instance, do we have to give a graph on n vertices to be sure that, no matter how these edges are arranged, the graph will contain a K r subgraph for some given r?
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Journal of Graph Theory, 1993
AbstractAn interval graph is said to be extremal if it achieves, among all interval graphs having the same number of vertices and the same clique number, the maximum possible number of edges. We give an intrinsic characterization of extremal interval graphs and derive recurrence relations for the numbers of such graphs.
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AbstractAn interval graph is said to be extremal if it achieves, among all interval graphs having the same number of vertices and the same clique number, the maximum possible number of edges. We give an intrinsic characterization of extremal interval graphs and derive recurrence relations for the numbers of such graphs.
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