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Wyszukujesz frazę "Henning, Michael" wg kryterium: Autor


Tytuł:
A characterization of roman trees
Autorzy:
Henning, Michael
Powiązania:
https://bibliotekanauki.pl/articles/743366.pdf
Data publikacji:
2002
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
dominating set
Roman dominating function
Opis:
A Roman dominating function (RDF) on a graph G = (V,E) is a function f: V → {0,1,2} satisfying the condition that every vertex u for which f(u) = 0 is adjacent to at least one vertex v for which f(v) = 2. The weight of f is $w(f) = ∑_{v ∈ V} f(v)$. The Roman domination number is the minimum weight of an RDF in G. It is known that for every graph G, the Roman domination number of G is bounded above by twice its domination number. Graphs which have Roman domination number equal to twice their domination number are called Roman graphs. At the Ninth Quadrennial International Conference on Graph Theory, Combinatorics, Algorithms, and Applications held at Western Michigan University in June 2000, Stephen T. Hedetniemi in his principal talk entitled "Defending the Roman Empire" posed the open problem of characterizing the Roman trees. In this paper, we give a characterization of Roman trees.
Źródło:
Discussiones Mathematicae Graph Theory; 2002, 22, 2; 325-334
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Graphs with large double domination numbers
Autorzy:
Henning, Michael
Powiązania:
https://bibliotekanauki.pl/articles/744277.pdf
Data publikacji:
2005
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
bounds
domination
double domination
minimum degree two
Opis:
In a graph G, a vertex dominates itself and its neighbors. A subset S ⊆ V(G) is a double dominating set of G if S dominates every vertex of G at least twice. The minimum cardinality of a double dominating set of G is the double domination number $γ_{×2}(G)$. If G ≠ C₅ is a connected graph of order n with minimum degree at least 2, then we show that $γ_{×2}(G) ≤ 3n/4$ and we characterize those graphs achieving equality.
Źródło:
Discussiones Mathematicae Graph Theory; 2005, 25, 1-2; 13-28
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bounds on Domination Parameters in Graphs: A Brief Survey
Autorzy:
Henning, Michael A.
Powiązania:
https://bibliotekanauki.pl/articles/32313552.pdf
Data publikacji:
2022-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
bounds
domination parameters
Opis:
In this paper we present a brief survey of bounds on selected domination parameters. We focus primarily on bounds on domination parameters in terms of the order and minimum degree of the graph. We present a list of open problems and conjectures that have yet to be solved in the hope of attracting future researchers to the field.
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 3; 665-708
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Trees with unique minimum total dominating sets
Autorzy:
Haynes, Teresa
Henning, Michael
Powiązania:
https://bibliotekanauki.pl/articles/743354.pdf
Data publikacji:
2002
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination
total domination
Opis:
A set S of vertices of a graph G is a total dominating set if every vertex of V(G) is adjacent to some vertex in S. We provide three equivalent conditions for a tree to have a unique minimum total dominating set and give a constructive characterization of such trees.
Źródło:
Discussiones Mathematicae Graph Theory; 2002, 22, 2; 233-246
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On double domination in graphs
Autorzy:
Harant, Jochen
Henning, Michael
Powiązania:
https://bibliotekanauki.pl/articles/744292.pdf
Data publikacji:
2005
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
average degree
bounds
double domination
probabilistic method
Opis:
In a graph G, a vertex dominates itself and its neighbors. A subset S ⊆ V(G) is a double dominating set of G if S dominates every vertex of G at least twice. The minimum cardinality of a double dominating set of G is the double domination number $γ_{×2}(G)$. A function f(p) is defined, and it is shown that $γ_{×2}(G) = min f(p)$, where the minimum is taken over the n-dimensional cube $Cⁿ = {p = (p₁,...,pₙ) | p_i ∈ IR, 0 ≤ p_i ≤ 1,i = 1,...,n}$. Using this result, it is then shown that if G has order n with minimum degree δ and average degree d, then $γ_{×2}(G) ≤ ((ln(1+d) + lnδ + 1)/δ)n$.
Źródło:
Discussiones Mathematicae Graph Theory; 2005, 25, 1-2; 29-34
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Characterization of Hypergraphs with Large Domination Number
Autorzy:
Henning, Michael A.
Löwenstein, Christian
Powiązania:
https://bibliotekanauki.pl/articles/31340924.pdf
Data publikacji:
2016-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination
transversal
hypergraph
Opis:
Let $ H = (V, E) $ be a hypergraph with vertex set $ V $ and edge set $ E $. A dominating set in $ H $ is a subset of vertices $ D \subseteq V $ such that for every vertex $ v \in V \ \backslash \ D $ there exists an edge $ \mathcal{e} \in E $ for which $ v \in \mathcal{e} $ and $ \mathcal{e} \cap D \ne \emptyset $. The domination number $ \gamma (H) $ is the minimum cardinality of a dominating set in $ H $. It is known [Cs. Bujtás, M.A. Henning and Zs. Tuza, Transversals and domination in uniform hypergraphs, European J. Combin. 33 (2012) 62-71] that for $ k \ge 5 $, if $ H $ is a hypergraph of order $ n $ and size $ m $ with all edges of size at least $ k $ and with no isolated vertex, then $ \gamma (H) \ge (n + \floor{ (k − 3)//2 } m) // ( \floor{ 3(k − 1)//2 } ) $. In this paper, we apply a recent result of the authors on hypergraphs with large transversal number [M.A. Henning and C. Löwenstein, A characterization of hypergraphs that achieve equality in the Chvátal-McDiarmid Theorem, Discrete Math. 323 (2014) 69-75] to characterize the hypergraphs achieving equality in this bound.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 2; 427-438
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bounds On The Disjunctive Total Domination Number Of A Tree
Autorzy:
Henning, Michael A.
Naicker, Viroshan
Powiązania:
https://bibliotekanauki.pl/articles/31341124.pdf
Data publikacji:
2016-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
total domination
disjunctive total domination
trees
Opis:
Let $G$ be a graph with no isolated vertex. In this paper, we study a parameter that is a relaxation of arguably the most important domination parameter, namely the total domination number, $ \gamma_t(G) $. A set $S$ of vertices in $G$ is a disjunctive total dominating set of $G$ if every vertex is adjacent to a vertex of $S$ or has at least two vertices in $S$ at distance 2 from it. The disjunctive total domination number, $ \gamma_t^d (G) $, is the minimum cardinality of such a set. We observe that $ \gamma_t^d (G) \ge \gamma_t (G) $. A leaf of $G$ is a vertex of degree 1, while a support vertex of $G$ is a vertex adjacent to a leaf. We show that if $T$ is a tree of order $n$ with $ \mathcal{l} $ leaves and $s$ support vertices, then $ 2(n−\mathcal{l}+3) // 5 \le \gamma_t^d (T) \le (n+s−1)//2 $ and we characterize the families of trees which attain these bounds. For every tree $T$, we show have $ \gamma_t(T) // \gamma_t^d (T) <2 $ and this bound is asymptotically tight.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 1; 153-171
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Domination Game: Extremal Families for the 3/5-Conjecture for Forests
Autorzy:
Henning, Michael A.
Löwenstein, Christian
Powiązania:
https://bibliotekanauki.pl/articles/31341965.pdf
Data publikacji:
2017-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination game
3/5 conjecture
Opis:
In the domination game on a graph $G$, the players Dominator and Staller alternately select vertices of $G$. Each vertex chosen must strictly increase the number of vertices dominated. This process eventually produces a dominating set of $G$; Dominator aims to minimize the size of this set, while Staller aims to maximize it. The size of the dominating set produced under optimal play is the game domination number of $G$, denoted by $ \gamma_g (G) $. Kinnersley, West and Zamani [SIAM J. Discrete Math. 27 (2013) 2090-2107] posted their 3/5-Conjecture that $ \gamma_g (G) \le 3/5 n $ for every isolate-free forest on n vertices. Brešar, Klavžar, Košmrlj and Rall [Discrete Appl. Math. 161 (2013) 1308-1316] presented a construction that yields an infinite family of trees that attain the conjectured 3/5-bound. In this paper, we provide a much larger, but simpler, construction of extremal trees. We conjecture that if $ G $ is an isolate-free forest on $ n $ vertices satisfying $ \gamma_g (G) = 3/5 n $, then every component of $G$ belongs to our construction.
Źródło:
Discussiones Mathematicae Graph Theory; 2017, 37, 2; 369-381
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Total Forcing Sets and Zero Forcing Sets in Trees
Autorzy:
Davila, Randy
Henning, Michael A.
Powiązania:
https://bibliotekanauki.pl/articles/31348333.pdf
Data publikacji:
2020-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
forcing set
forcing number
total forcing set
total forcing number
Opis:
A dynamic coloring of the vertices of a graph $G$ starts with an initial subset $S$ of colored vertices, with all remaining vertices being non-colored. At each discrete time interval, a colored vertex with exactly one non-colored neighbor forces this non-colored neighbor to be colored. The initial set $S$ is called a forcing set of $G$ if, by iteratively applying the forcing process, every vertex in $G$ becomes colored. If the initial set $S$ has the added property that it induces a subgraph of $G$ without isolated vertices, then $S$ is called a total forcing set in $G$. The minimum cardinality of a total forcing set in $G$ is its total forcing number, denoted $F_t(G)$. We prove that if $T$ is a tree of order $n ≥ 3$ with maximum degree $Δ$ and with $n_1$ leaves, then $n_1≤F_t(T)≤1/Δ((Δ-1)n+1)$. In both lower and upper bounds, we characterize the infinite family of trees achieving equality. Further we show that $F_t(T) ≥ F (T) + 1$, and we characterize the extremal trees for which equality holds.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 3; 733-754
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Minimal Graphs with Disjoint Dominating and Paired-Dominating Sets
Autorzy:
Henning, Michael A.
Topp, Jerzy
Powiązania:
https://bibliotekanauki.pl/articles/32222686.pdf
Data publikacji:
2021-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination
paired-domination
Opis:
A subset D ⊆ VG is a dominating set of G if every vertex in VG – D has a neighbor in D, while D is a paired-dominating set of G if D is a dominating set and the subgraph induced by D contains a perfect matching. A graph G is a DPDP -graph if it has a pair (D, P) of disjoint sets of vertices of G such that D is a dominating set and P is a paired-dominating set of G. The study of the DPDP -graphs was initiated by Southey and Henning [Cent. Eur. J. Math. 8 (2010) 459–467; J. Comb. Optim. 22 (2011) 217–234]. In this paper, we provide conditions which ensure that a graph is a DPDP -graph. In particular, we characterize the minimal DPDP -graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 3; 827-847
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Graphs with Disjoint Dominating and 2-Dominating Sets
Autorzy:
Henning, Michael A.
Rall, Douglas F.
Powiązania:
https://bibliotekanauki.pl/articles/30146715.pdf
Data publikacji:
2013-03-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination
2-domination
vertex partition
Opis:
A DD2-pair of a graph G is a pair (D,D2) of disjoint sets of vertices of G such that D is a dominating set and D2 is a 2-dominating set of G. Although there are infinitely many graphs that do not contain a DD2-pair, we show that every graph with minimum degree at least two has a DD2-pair. We provide a constructive characterization of trees that have a DD2-pair and show that K3,3 is the only connected graph with minimum degree at least three for which D ∪ D2 necessarily contains all vertices of the graph.
Źródło:
Discussiones Mathematicae Graph Theory; 2013, 33, 1; 139-146
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Total domination subdivision numbers of graphs
Autorzy:
Haynes, Teresa
Henning, Michael
Hopkins, Lora
Powiązania:
https://bibliotekanauki.pl/articles/744561.pdf
Data publikacji:
2004
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
total domination number
total domination subdivision number
Opis:
A set S of vertices in a graph G = (V,E) is a total dominating set of G if every vertex of V is adjacent to a vertex in S. The total domination number of G is the minimum cardinality of a total dominating set of G. The total domination subdivision number of G is the minimum number of edges that must be subdivided (where each edge in G can be subdivided at most once) in order to increase the total domination number. First we establish bounds on the total domination subdivision number for some families of graphs. Then we show that the total domination subdivision number of a graph can be arbitrarily large.
Źródło:
Discussiones Mathematicae Graph Theory; 2004, 24, 3; 457-467
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vertices Contained In All Or In No Minimum Semitotal Dominating Set Of A Tree
Autorzy:
Henning, Michael A.
Marcon, Alister J.
Powiązania:
https://bibliotekanauki.pl/articles/31341173.pdf
Data publikacji:
2016-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination
semitotal domination
trees
Opis:
Let G be a graph with no isolated vertex. In this paper, we study a parameter that is squeezed between arguably the two most important domination parameters; namely, the domination number, γ(G), and the total domination number, γt(G). A set S of vertices in a graph G is a semitotal dominating set of G if it is a dominating set of G and every vertex in S is within distance 2 of another vertex of S. The semitotal domination number, γt2(G), is the minimum cardinality of a semitotal dominating set of G. We observe that γ(G) ≤ γt2(G) ≤ γt(G). We characterize the set of vertices that are contained in all, or in no minimum semitotal dominating set of a tree.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 1; 71-93
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nordhaus-Gaddum bounds for upper total domination
Autorzy:
Haynes, Teresa W.
Henning, Michael A.
Powiązania:
https://bibliotekanauki.pl/articles/2216175.pdf
Data publikacji:
2022
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
upper total domination
Nordhaus-Gaddum bound
Opis:
A set S of vertices in an isolate-free graph G is a total dominating set if every vertex in G is adjacent to a vertex in S. A total dominating set of G is minimal if it contains no total dominating set of $\bar{G}$ as a proper subset. The upper total domination number $Γ_t(G)$ of G is the maximum cardinality of a minimal total dominating set in G. We establish Nordhaus-Gaddum bounds involving the upper total domination numbers of a graph G and its complement $\bar{G}$. We prove that if G is a graph of order n such that both G and $\bar{G}$ are isolate-free, then $Γ_t(G) + Γ_t(\bar{G}) ≤ n + 2$ and $Γ_t(G)Γ_t(\bar{G}) ≤ 1/4 (n + 2)^2$, and these bounds are tight.
Źródło:
Opuscula Mathematica; 2022, 42, 4; 573-582
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Partitioning a graph into a dominating set, a total dominating set, and something else
Autorzy:
Henning, Michael
Löwenstein, Christian
Rautenbach, Dieter
Powiązania:
https://bibliotekanauki.pl/articles/744065.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination
total domination
domatic number
vertex partition
Petersen graph
Opis:
A recent result of Henning and Southey (A note on graphs with disjoint dominating and total dominating set, Ars Comb. 89 (2008), 159-162) implies that every connected graph of minimum degree at least three has a dominating set D and a total dominating set T which are disjoint. We show that the Petersen graph is the only such graph for which D∪T necessarily contains all vertices of the graph.
Źródło:
Discussiones Mathematicae Graph Theory; 2010, 30, 4; 563-574
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł

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