Results 71 to 80 of about 131 (107)

New Bounds for Codes Identifying Vertices in Graphs

open access: yes, 1999
Let G = (V; E) be an undirected graph. Let C be a subset of vertices that we shall call a code. For any vertex v 2 V , the neighbouring set N(v; C) is the set of vertices of C at distance at most one from v.
Gerard Cohen   +3 more
core  

A sharp lower bound on the signless Laplacian index of graphs with (κ,τ)-regular sets

open access: yesSpecial Matrices, 2018
A new lower bound on the largest eigenvalue of the signless Laplacian spectra for graphs with at least one (κ,τ)regular set is introduced and applied to the recognition of non-Hamiltonian graphs or graphs without a perfect matching.
Andeelić Milica   +2 more
doaj   +1 more source

Robust Matchings, Maximum Clustering, and Maximum Capacitated Medians

open access: yes, 1999
We consider complete graphs with nonnegative edge weights. A p-matching is a set of p disjoint edges. We prove the existence of a maximal (with respect to inclusion) matching M that contains for any p jM j p edges whose total weight is at least 1 p 2
Refael Hassin, Shlomi Rubinstein
core  

C7-Decompositions of the Tensor Product of Complete Graphs

open access: yesDiscussiones Mathematicae Graph Theory, 2017
In this paper we consider a decomposition of Km × Kn, where × denotes the tensor product of graphs, into cycles of length seven. We prove that for m, n ≥ 3, cycles of length seven decompose the graph Km × Kn if and only if (1) either m or n is odd and (2)
Manikandan R.S., Paulraja P.
doaj   +1 more source

Matching criticality in intersecting hypergraphs

open access: yes, 2017
The transversal number τ(H) of a hypergraph H is the minimum cardinality of a set of vertices that intersects all edges of H. The matching number α′(H) of H is the maximum cardinality of a matching in H. A hypergraph H is intersecting if and only if α′(H)
Ni, Zhenyu, Shan, Erfang, Kang, Liying
core  

Further results on enumeration of perfect matchings of Cartesian product graphs

open access: yesOpen Mathematics
Counting perfect matchings is an interesting and challenging combinatorial task. It has important applications in statistical physics and chemistry. As the general problem is #P-complete, it is usually tackled by randomized heuristics and approximation ...
Wu Tingzeng, Zeng Xiaolin
doaj   +1 more source

On Properties of Distance-Based Entropies on Fullerene Graphs. [PDF]

open access: yesEntropy (Basel), 2019
Ghorbani M   +4 more
europepmc   +1 more source

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