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Wyszukujesz frazę "tree connectivity" wg kryterium: Temat


Wyświetlanie 1-5 z 5
Tytuł:
On Two Generalized Connectivities of Graphs
Autorzy:
Sun, Yuefang
Li, Fengwei
Jin, Zemin
Powiązania:
https://bibliotekanauki.pl/articles/31342427.pdf
Data publikacji:
2018-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
k -connectivity
pendant tree-connectivity
Cartesian product
Cayley graph
Opis:
The concept of generalized $k$-connectivity $ \kappa_k (G) $, mentioned by Hager in 1985, is a natural generalization of the path-version of the classical connectivity. The pendant tree-connectivity $ \tau_k (G) $ was also introduced by Hager in 1985, which is a specialization of generalized $k$-connectivity but a generalization of the classical connectivity. Another generalized connectivity of a graph $G$, named $k$-connectivity $ \kappa_k^' (G) $, introduced by Chartrand et al. in 1984, is a generalization of the cut-version of the classical connectivity. In this paper, we get the lower and upper bounds for the difference of $ \kappa_k^' (G) $ and $ \tau_k(G) $ by showing that for a connected graph $G$ of order $n$, if $ \kappa_k^' (G) \ne n − k + 1 $ where $ k \ge 3 $, then $ 1 \le \kappa_k^' (G) − \tau_k (G) \le n − k $; otherwise, $ 1 \le κ_k^' (G) − \tau_k(G) \le n − k + 1 $. Moreover, all of these bounds are sharp. We get a sharp upper bound for the 3-connectivity of the Cartesian product of any two connected graphs with orders at least 5. Especially, the exact values for some special cases are determined. Among our results, we also study the pendant tree-connectivity of Cayley graphs on Abelian groups of small degrees and obtain the exact values for $ \tau_k(G) $, where $G$ is a cubic or 4-regular Cayley graph on Abelian groups, $ 3 \le k \le n $.
Źródło:
Discussiones Mathematicae Graph Theory; 2018, 38, 1; 245-261
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Minimum Size of a Graph with Given Tree Connectivity
Autorzy:
Sun, Yuefang
Sheng, Bin
Jin, Zemin
Powiązania:
https://bibliotekanauki.pl/articles/32083875.pdf
Data publikacji:
2021-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
generalized connectivity
tree connectivity
eneralized k-connectivity
generalized k-edge-connectivity
packing
Opis:
For a graph $G = (V, E)$ and a set $S ⊆ V$ of at least two vertices, an $S$-tree is a such subgraph $T$ of $G$ that is a tree with $S ⊆ V(T)$. Two $S$-trees $T_1$ and $T_2$ are said to be internally disjoint if $E(T_1) ∩ E(T_2) = ∅$ and $V(T_1) ∩ V(T_2) = S$, and edge-disjoint if $E(T_1) ∩ E(T_2) = ∅$. The generalized local connectivity $κ_G(S)$ (generalized local edge-connectivity $λ_G(S)$, respectively) is the maximum number of internally disjoint (edge-disjoint, respectively) $S$-trees in $G$. For an integer $k$ with $2 ≤ k ≤ n$, the generalized $k$-connectivity (generalized $k$-edge-connectivity, respectively) is defined as $κ_k(G) = min{κ_G(S) | S ⊆ V(G), |S| = k} (λ_k(G) = min{λ_G(S) | S ⊆ V(G), |S| = k}$, respectively). Let $f(n, k, t)$ ($g(n, k, t)$, respectively) be the minimum size of a connected graph $G$ with order $n$ and $κ_k(G) = t$ ($λ_k(G) = t$, respectively), where $3 ≤ k ≤ n$ and \(1≤t≤n-⌈\frac{k}{2}⌉\). For general $k$ and $t$, Li and Mao obtained a lower bound for $g(n, k, t)$ which is tight for the case $k = 3$. We show that the bound also holds for $f(n, k, t)$ and is tight for the case $k = 3$. When t is general, we obtain upper bounds of both $f(n, k, t)$ and $g(n, k, t)$ for $k ∈ {3, 4, 5}$, and all of these bounds can be attained. When $k$ is general, we get an upper bound of $g(n, k, t)$ for $t ∈ {1, 2, 3, 4}$ and an upper bound of $f(n, k, t)$ for $t ∈ {1, 2, 3}$. Moreover, both bounds can be attained.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 2; 409-425
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spectral integral variation of trees
Autorzy:
Wang, Yi
Fan, Yi-Zheng
Powiązania:
https://bibliotekanauki.pl/articles/743873.pdf
Data publikacji:
2006
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
tree
Laplacian eigenvalues
spectral integral variation
algebraic connectivity
Opis:
In this paper, we determine all trees with the property that adding a particular edge will result in exactly two Laplacian eigenvalues increasing respectively by 1 and the other Laplacian eigenvalues remaining fixed. We also investigate a situation in which the algebraic connectivity is one of the changed eigenvalues.
Źródło:
Discussiones Mathematicae Graph Theory; 2006, 26, 1; 49-58
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Graphs with Large Generalized (Edge-)Connectivity
Autorzy:
Li, Xueliang
Mao, Yaping
Powiązania:
https://bibliotekanauki.pl/articles/31340594.pdf
Data publikacji:
2016-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
(edge-)connectivity
Steiner tree
internally disjoint trees
edge-disjoint trees
packing
generalized (edge-)connectivity
Opis:
The generalized $k$-connectivity $ \kappa_k (G) $ of a graph $G$, introduced by Hager in 1985, is a nice generalization of the classical connectivity. Recently, as a natural counterpart, we proposed the concept of generalized $k$-edge-connectivity $ \lambda_k (G)$. In this paper, graphs of order $n$ such that $ \kappa_k (G) = n - k/2 - 1 $ and $ \lambda_k (G) = n - k/2 - 1 $ for even $k$ are characterized.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 4; 931-958
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Vertex-Rainbow Index of A Graph
Autorzy:
Mao, Yaping
Powiązania:
https://bibliotekanauki.pl/articles/31340818.pdf
Data publikacji:
2016-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
vertex-coloring
connectivity
vertex-rainbow S-tree
vertex- rainbow index
Nordhaus-Gaddum type
Opis:
The k-rainbow index rxk(G) of a connected graph G was introduced by Chartrand, Okamoto and Zhang in 2010. As a natural counterpart of the k-rainbow index, we introduce the concept of k-vertex-rainbow index rvxk(G) in this paper. In this paper, sharp upper and lower bounds of rvxk(G) are given for a connected graph G of order n, that is, 0 ≤ rvxk(G) ≤ n − 2. We obtain Nordhaus-Gaddum results for 3-vertex-rainbow index of a graph G of order n, and show that rvx3(G) + rvx3(Ḡ) = 4 for n = 4 and 2 ≤ rvx3(G) + rvx3(Ḡ) ≤ n − 1 for n ≥ 5. Let t(n, k, ℓ) denote the minimal size of a connected graph G of order n with rvxk(G) ≤ ℓ, where 2 ≤ ℓ ≤ n − 2 and 2 ≤ k ≤ n. Upper and lower bounds on t(n, k, ℓ) are also obtained.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 3; 669-681
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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