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Wyświetlanie 1-11 z 11
Tytuł:
Undirected and directed graphs with near polynomial growth
Autorzy:
Trofimov, V.
Powiązania:
https://bibliotekanauki.pl/articles/743188.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
vertex-symmetric graph
vertex-symmetric directed graph
near polynomial growth
multivalued mapping
Opis:
The growth function of a graph with respect to a vertex is near polynomial if there exists a polynomial bounding it above for infinitely many positive integers. In the paper vertex-symmetric undirected graphs and vertex-symmetric directed graphs with coinciding in- and out-degrees are described in the case their growth functions are near polynomial.
Źródło:
Discussiones Mathematicae Graph Theory; 2003, 23, 2; 383-391
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Twin Minus Total Domination Numbers In Directed Graphs
Autorzy:
Dehgardi, Nasrin
Atapour, Maryam
Powiązania:
https://bibliotekanauki.pl/articles/31341587.pdf
Data publikacji:
2017-11-27
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
twin minus total dominating function
twin minus total domination number
directed graph
Opis:
Let $ D = (V,A) $ be a finite simple directed graph (shortly, digraph). A function $ f : V \rightarrow {−1, 0, 1} $ is called a twin minus total dominating function (TMTDF) if $ f(N^−(v)) \ge 1 $ and $ f(N^+(v)) \ge 1 $ for each vertex $ v \in V $. The twin minus total domination number of $D$ is $\gamma_{mt}^\ast (D) = \text{min} \{ w(f) | f $ is a TMTDF of $ D \} $. In this paper, we initiate the study of twin minus total domination numbers in digraphs and we present some lower bounds for $ \gamma_{mt}^\ast (D) $ in terms of the order, size and maximum and minimum in-degrees and out-degrees. In addition, we determine the twin minus total domination numbers of some classes of digraphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2017, 37, 4; 989-1004
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On independent sets and non-augmentable paths in directed graphs
Autorzy:
Galeana-Sánchez, H.
Powiązania:
https://bibliotekanauki.pl/articles/744219.pdf
Data publikacji:
1998
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
digraph
independent set
directed path
non-augmentable path
Opis:
We investigate sufficient conditions, and in case that D be an asymmetrical digraph a necessary and sufficient condition for a digraph to have the following property: "In any induced subdigraph H of D, every maximal independent set meets every non-augmentable path". Also we obtain a necessary and sufficient condition for any orientation of a graph G results a digraph with the above property. The property studied in this paper is an instance of the property of a conjecture of J.M. Laborde, Ch. Payan and N.H. Huang: "Every digraph contains an independent set which meets every longest directed path" (1982).
Źródło:
Discussiones Mathematicae Graph Theory; 1998, 18, 2; 171-181
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On maximal finite antichains in the homomorphism order of directed graphs
Autorzy:
Nesetril, Jaroslav
Tardif, Claude
Powiązania:
https://bibliotekanauki.pl/articles/743175.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
chromatic number
homomorphism duality
Opis:
We show that the pairs ${T,D_T}$ where T is a tree and $D_T$ its dual are the only maximal antichains of size 2 in the category of directed graphs endowed with its natural homomorphism ordering.
Źródło:
Discussiones Mathematicae Graph Theory; 2003, 23, 2; 325-332
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Factoring directed graphs with respect to the cardinal product in polynomial time
Autorzy:
Imrich, Wilfried
Klöckl, Werner
Powiązania:
https://bibliotekanauki.pl/articles/743472.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
directed graphs
cardinal product
graph algorithms
Opis:
By a result of McKenzie [4] finite directed graphs that satisfy certain connectivity and thinness conditions have the unique prime factorization property with respect to the cardinal product. We show that this property still holds under weaker connectivity and stronger thinness conditions. Furthermore, for such graphs the factorization can be determined in polynomial time.
Źródło:
Discussiones Mathematicae Graph Theory; 2007, 27, 3; 593-601
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Factoring directed graphs with respect to the cardinal product in polynomial time II
Autorzy:
Imrich, Wilfried
Klöckl, Werner
Powiązania:
https://bibliotekanauki.pl/articles/744038.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
directed graphs
cardinal product
graph algorithms
Opis:
By a result of McKenzie [7] all finite directed graphs that satisfy certain connectivity conditions have unique prime factorizations with respect to the cardinal product. McKenzie does not provide an algorithm, and even up to now no polynomial algorithm that factors all graphs satisfying McKenzie's conditions is known. Only partial results [1,3,5] have been published, all of which depend on certain thinness conditions of the graphs to be factored.
In this paper we weaken the thinness conditions and thus significantly extend the class of graphs for which the prime factorization can be found in polynomial time.
Źródło:
Discussiones Mathematicae Graph Theory; 2010, 30, 3; 461-474
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On L(2, 1)-Labelings of Oriented Graphs
Autorzy:
Colucci, Lucas
Győri, Ervin
Powiązania:
https://bibliotekanauki.pl/articles/32361754.pdf
Data publikacji:
2022-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
L (2,1)-labeling
directed graphs
Opis:
We extend a result of Griggs and Yeh about the maximum possible value of the L(2, 1)-labeling number of a graph in terms of its maximum degree to oriented graphs. We consider the problem both in the usual definition of the oriented L(2, 1)-labeling number and in some variants we introduce.
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 1; 39-46
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tr -Span of Directed Wheel Graphs
Autorzy:
Besson, Marc
Tesman, Barry
Powiązania:
https://bibliotekanauki.pl/articles/31342270.pdf
Data publikacji:
2018-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
T -coloring
digraph
wheel graph
span
Opis:
In this paper, we consider T-colorings of directed graphs. In particular, we consider as a T-set the set Tr = {0, 1, 2, . . ., r−1, r+1, . . .}. Exact values and bounds of the Tr-span of directed graphs whose underlying graph is a wheel graph are presented.
Źródło:
Discussiones Mathematicae Graph Theory; 2018, 38, 4; 871-888
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Isomorphisms and traversability of directed path graphs
Autorzy:
Broersma, Hajo
Li, Xueliang
Powiązania:
https://bibliotekanauki.pl/articles/743350.pdf
Data publikacji:
2002
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
directed path graph
line digraph
isomorphism
travers-ability
Opis:
The concept of a line digraph is generalized to that of a directed path graph. The directed path graph Pₖ(D) of a digraph D is obtained by representing the directed paths on k vertices of D by vertices. Two vertices are joined by an arc whenever the corresponding directed paths in D form a directed path on k+1 vertices or form a directed cycle on k vertices in D. In this introductory paper several properties of P₃(D) are studied, in particular with respect to isomorphism and traversability. In our main results, we characterize all digraphs D with P₃(D) ≅ D, we show that P₃(D₁) ≅ P₃(D₂) "almost always" implies D₁ ≅ D₂, and we characterize all digraphs with Eulerian or Hamiltonian P₃-graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2002, 22, 2; 215-228
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Circuit bases of strongly connected digraphs
Autorzy:
Gleiss, Petra
Leydold, Josef
Stadler, Peter
Powiązania:
https://bibliotekanauki.pl/articles/743155.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
directed graphs
cycle space
relevant circuits
minimum length basis
Opis:
The cycle space of a strongly connected graph has a basis consisting of directed circuits. The concept of relevant circuits is introduced as a generalization of the relevant cycles in undirected graphs. A polynomial time algorithm for the computation of a minimum weight directed circuit basis is outlined.
Źródło:
Discussiones Mathematicae Graph Theory; 2003, 23, 2; 241-260
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Metric Dimension of Directed and Undirected Circulant Graphs
Autorzy:
Vetrík, Tomáš
Powiązania:
https://bibliotekanauki.pl/articles/31870010.pdf
Data publikacji:
2020-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
metric dimension
resolving set
circulant graph
distance
Opis:
The undirected circulant graph $C_n(±1, ±2, . . ., ±t)$ consists of vertices $v_0, v_1, . . ., v_{n−1}$ and undirected edges $v_iv_{i+j}$, where $0 ≤ i ≤ n − 1, 1 ≤ j ≤ t (2 ≤ t ≤ \frac{n}{2})$, and the directed circulant graph $C_n(1, t)$ consists of vertices $v_0, v_1, . . ., v_{n−1}$ and directed edges $v_iv_{i+1}, v_iv_{i+t}$, where $0 ≤ i ≤ n − 1 (2 ≤ t ≤ n−1)$, the indices are taken modulo $n$. Results on the metric dimension of undirected circulant graphs $C_n(±1, ±t)$ are available only for special values of $t$. We give a complete solution of this problem for directed graphs $C_n(1, t)$ for every $t ≥ 2$ if $n ≥ 2t^2$. Grigorious et al. [On the metric dimension of circulant and Harary graphs, Appl. Math. Comput. 248 (2014) 47–54] presented a conjecture saying that dim $(C_n(±1, ±2, . . ., ±t)) = t + p − 1$ for $n = 2tk + t + p$, where $3 ≤ p ≤ t + 1$. We disprove it by showing that dim $(C_n(±1, ±2, . . ., ±t)) ≤ t + \frac{p+1}{2}$ for $n = 2tk + t + p$, where $t ≥ 4$ is even, $p$ is odd, $1 ≤ p ≤ t + 1$ and $k ≥ 1$.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 1; 67-76
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-11 z 11

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