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A Note on Non-Dominating Set Partitions in Graphs

Wyatt J. Desormeaux, Teresa W. Haynes, Michael A. Henning (2016)

Discussiones Mathematicae Graph Theory

A set S of vertices of a graph G is a dominating set if every vertex not in S is adjacent to a vertex of S and is a total dominating set if every vertex of G is adjacent to a vertex of S. The cardinality of a minimum dominating (total dominating) set of G is called the domination (total domination) number. A set that does not dominate (totally dominate) G is called a non-dominating (non-total dominating) set of G. A partition of the vertices of G into non-dominating (non-total dominating) sets is...

A note on on-line ranking number of graphs

Gabriel Semanišin, Roman Soták (2006)

Czechoslovak Mathematical Journal

A k -ranking of a graph G = ( V , E ) is a mapping ϕ V { 1 , 2 , , k } such that each path with endvertices of the same colour c contains an internal vertex with colour greater than c . The ranking number of a graph G is the smallest positive integer k admitting a k -ranking of G . In the on-line version of the problem, the vertices v 1 , v 2 , , v n of G arrive one by one in an arbitrary order, and only the edges of the induced graph G [ { v 1 , v 2 , , v i } ] are known when the colour for the vertex v i has to be chosen. The on-line ranking number of a graph G is the smallest...

A note on packing of two copies of a hypergraph

Monika Pilśniak, Mariusz Woźniak (2007)

Discussiones Mathematicae Graph Theory

A 2-packing of a hypergraph 𝓗 is a permutation σ on V(𝓗) such that if an edge e belongs to 𝓔(𝓗), then σ (e) does not belong to 𝓔(𝓗). We prove that a hypergraph which does not contain neither empty edge ∅ nor complete edge V(𝓗) and has at most 1/2n edges is 2-packable. A 1-uniform hypergraph of order n with more than 1/2n edges shows that this result cannot be improved by increasing the size of 𝓗.

A Note on Path Domination

Liliana Alcón (2016)

Discussiones Mathematicae Graph Theory

We study domination between different types of walks connecting two non-adjacent vertices u and v of a graph (shortest paths, induced paths, paths, tolled walks). We succeeded in characterizing those graphs in which every uv-walk of one particular kind dominates every uv-walk of other specific kind. We thereby obtained new characterizations of standard graph classes like chordal, interval and superfragile graphs.

A note on perfect matchings in uniform hypergraphs with large minimum collective degree

Vojtěch Rödl, Andrzej Ruciński, Mathias Schacht, Endre Szemerédi (2008)

Commentationes Mathematicae Universitatis Carolinae

For an integer k 2 and a k -uniform hypergraph H , let δ k - 1 ( H ) be the largest integer d such that every ( k - 1 ) -element set of vertices of H belongs to at least d edges of H . Further, let t ( k , n ) be the smallest integer t such that every k -uniform hypergraph on n vertices and with δ k - 1 ( H ) t contains a perfect matching. The parameter t ( k , n ) has been completely determined for all k and large n divisible by k by Rödl, Ruci’nski, and Szemerédi in [Perfect matchings in large uniform hypergraphs with large minimum collective degree, submitted]....

A note on periodicity of the 2-distance operator

Bohdan Zelinka (2000)

Discussiones Mathematicae Graph Theory

The paper solves one problem by E. Prisner concerning the 2-distance operator T₂. This is an operator on the class C f of all finite undirected graphs. If G is a graph from C f , then T₂(G) is the graph with the same vertex set as G in which two vertices are adjacent if and only if their distance in G is 2. E. Prisner asks whether the periodicity ≥ 3 is possible for T₂. In this paper an affirmative answer is given. A result concerning the periodicity 2 is added.

A note on pm-compact bipartite graphs

Jinfeng Liu, Xiumei Wang (2014)

Discussiones Mathematicae Graph Theory

A graph is called perfect matching compact (briefly, PM-compact), if its perfect matching graph is complete. Matching-covered PM-compact bipartite graphs have been characterized. In this paper, we show that any PM-compact bipartite graph G with δ (G) ≥ 2 has an ear decomposition such that each graph in the decomposition sequence is also PM-compact, which implies that G is matching-covered

A note on q -partial difference equations and some applications to generating functions and q -integrals

Da-Wei Niu, Jian Cao (2019)

Czechoslovak Mathematical Journal

We study the condition on expanding an analytic several variables function in terms of products of the homogeneous generalized Al-Salam-Carlitz polynomials. As applications, we deduce bilinear generating functions for the homogeneous generalized Al-Salam-Carlitz polynomials. We also gain multilinear generating functions for the homogeneous generalized Al-Salam-Carlitz polynomials. Moreover, we obtain generalizations of Andrews-Askey integrals and Ramanujan q -beta integrals. At last, we derive U ( n + 1 ) ...

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