Displaying similar documents to “Relations between ( κ , τ ) -regular sets and star complements”

On graphs with the largest Laplacian index

Bo Lian Liu, Zhibo Chen, Muhuo Liu (2008)

Czechoslovak Mathematical Journal

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Let G be a connected simple graph on n vertices. The Laplacian index of G , namely, the greatest Laplacian eigenvalue of G , is well known to be bounded above by n . In this paper, we give structural characterizations for graphs G with the largest Laplacian index n . Regular graphs, Hamiltonian graphs and planar graphs with the largest Laplacian index are investigated. We present a necessary and sufficient condition on n and k for the existence of a k -regular graph G of order n with the...

Results on F -continuous graphs

Anna Draganova (2009)

Czechoslovak Mathematical Journal

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For any nontrivial connected graph F and any graph G , the of a vertex v in G is the number of copies of F in G containing v . G is called if and only if the F -degrees of any two adjacent vertices in G differ by at most 1; G is if the F -degrees of all vertices in G are the same. This paper classifies all P 4 -continuous graphs with girth greater than 3. We show that for any nontrivial connected graph F other than the star K 1 , k , k 1 , there exists a regular graph that is not F -continuous. If...

Cores and shells of graphs

Allan Bickle (2013)

Mathematica Bohemica

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The k -core of a graph G , C k ( G ) , is the maximal induced subgraph H G such that δ ( G ) k , if it exists. For k > 0 , the k -shell of a graph G is the subgraph of G induced by the edges contained in the k -core and not contained in the ( k + 1 ) -core. The core number of a vertex is the largest value for k such that v C k ( G ) , and the maximum core number of a graph, C ^ ( G ) , is the maximum of the core numbers of the vertices of G . A graph G is k -monocore if C ^ ( G ) = δ ( G ) = k . This paper discusses some basic results on the structure of k -cores and...

Equienergetic self-complementary graphs

G. Indulal, A. Vijayakumar (2008)

Czechoslovak Mathematical Journal

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In this paper equienergetic self-complementary graphs on p vertices for every p = 4 k , k 2 and p = 24 t + 1 , t 3 are constructed.