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Wyświetlanie 1-13 z 13
Tytuł:
On the structure of compact graphs
Autorzy:
Nikandish, R.
Shaveisi, F.
Powiązania:
https://bibliotekanauki.pl/articles/255638.pdf
Data publikacji:
2017
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
compact graph
vertex degree
cycle
neighborhood
Opis:
A simple graph G is called a compact graph if G contains no isolated vertices and for each pair x, y of non-adjacent vertices of G, there is a vertex z with N(x) ∪ N(y) ⊆ N(z), where N(v) is the neighborhood of v, for every vertex v of G. In this paper, compact graphs with sufficient number of edges are studied. Also, it is proved that every regular compact graph is strongly regular. Some results about cycles in compact graphs are proved, too. Among other results, it is proved that if the ascending chain condition holds for the set of neighbors of a compact graph G, then the descending chain condition holds for the set of neighbors of G.
Źródło:
Opuscula Mathematica; 2017, 37, 6; 875-886
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the multiplicative Zagreb coindex of graphs
Autorzy:
Xu, K.
Das, K. Ch.
Tang, K.
Powiązania:
https://bibliotekanauki.pl/articles/254706.pdf
Data publikacji:
2013
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
vertex degree
tree
upper or lower bound
Opis:
For a (molecular) graph G with vertex set V (G) and edge set E(G), the first and second Zagreb indices of G are defined as [formula] and [formula] respectively, where dG(v) is the degree of vertex v in G. The alternative expression of M1 (G) is [formula]. Recently Ashrafi, Doslic and Hamzeh introduced two related graphical invariants [formula] and [formula] named as first Zagreb coindex and second Zagreb coindex, respectively. Here we define two new graphical invariants [formula] and [formula] as the respective multiplicative versions of [formula]. In this paper, we have reported some properties, especially upper and lower bounds, for these two graph invariants of connected (molecular) graphs. Moreover, some corresponding extremal graphs have been characterized with respect to these two indices.
Źródło:
Opuscula Mathematica; 2013, 33, 1; 191-204
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Families of triples with high minimum degree are Hamiltonian
Autorzy:
Rödl, Vojtech
Ruciński, Andrzej
Powiązania:
https://bibliotekanauki.pl/articles/30148238.pdf
Data publikacji:
2014-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
3-uniform hypergraph
Hamilton cycle
minimum vertex degree
Opis:
In this paper we show that every family of triples, that is, a 3-uniform hypergraph, with minimum degree at least $$(\frac{5−√5}{3} + γ)\binom{n−1}{2}$$ contains a tight Hamiltonian cycle.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 2; 361-381
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An application of graph theory to linguistic complexity
Autorzy:
Piperski, Alexander
Powiązania:
https://bibliotekanauki.pl/articles/1151871.pdf
Data publikacji:
2014
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
linguistic complexity
morphology
graph theory
average vertex degree
Opis:
This article introduces a new measure of linguistic complexity which is based on the dual nature of the linguistic sign. Complexity is analyzed as consisting of three components, namely the conceptual complexity (complexity of the signified), the formal complexity (complexity of the signifier) and the form-meaning correspondence complexity. I describe a way of plotting the form-meaning relationship on a graph with two tiers (the form tier and the meaning tier) and apply a complexity measure from graph theory (average vertex degree) to assess the complexity of such graphs. The proposed method is illustrated by estimating the complexity of full noun phrases (determiner + adjective + noun) in English, Swedish, and German. I also mention the limitations and the problems which might arise when using this method.
Źródło:
Yearbook of the Poznań Linguistic Meeting; 2014, 1, 1
2449-7525
Pojawia się w:
Yearbook of the Poznań Linguistic Meeting
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An application of graph theory to linguistic complexity
Autorzy:
Piperski, Alexander
Powiązania:
https://bibliotekanauki.pl/articles/2135360.pdf
Data publikacji:
2014-11-19
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
linguistic complexity
morphology
graph theory
average vertex degree
Opis:
This article introduces a new measure of linguistic complexity which is based on the dual nature of the linguistic sign. Complexity is analyzed as consisting of three components, namely the conceptual complexity (complexity of the signified), the formal complexity (complexity of the signifier) and the form-meaning correspondence complexity. I describe a way of plotting the form-meaning relationship on a graph with two tiers (the form tier and the meaning tier) and apply a complexity measure from graph theory (average vertex degree) to assess the complexity of such graphs. The proposed method is illustrated by estimating the complexity of full noun phrases (determiner + adjective + noun) in English, Swedish, and German. I also mention the limitations and the problems which might arise when using this method.
Źródło:
Yearbook of the Poznań Linguistic Meeting; 2014, 1, 1; 89-102
2449-7525
Pojawia się w:
Yearbook of the Poznań Linguistic Meeting
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
5-stars of low weight in normal plane maps with minimum degree 5
Autorzy:
Borodin, Oleg V.
Ivanova, Anna O.
Jensen, Tommy R.
Powiązania:
https://bibliotekanauki.pl/articles/30148303.pdf
Data publikacji:
2014-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graph
plane map
vertex degree
weight
light subgraph
Opis:
It is known that there are normal plane maps $M_5$ with minimum degree 5 such that the minimum degree-sum $w(S_5)$ of 5-stars at 5-vertices is arbitrarily large. In 1940, Lebesgue showed that if an $M_5$ has no 4-stars of cyclic type (5, 6, 6, 5) centered at 5-vertices, then $w(S_5) ≤ 68$. We improve this bound of 68 to 55 and give a construction of a (5, 6, 6, 5)-free $M_5$ with $w(S_5) = 48$.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 3; 539-546
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Open support of some special types of graphs under addition
Autorzy:
Jeyalakshmi, M.
Meena, N.
Powiązania:
https://bibliotekanauki.pl/articles/1193410.pdf
Data publikacji:
2021
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
degree of a vertex
open neighbourhood of a vertex
open support of a graph
open support of a vertex
Opis:
A open support of a vertex v under addition is defined by ∑_(u ∈N(v))▒deg〖(u)〗 and it is denoted by supp(v). A open support of a graph under addition is defined by ∑_(v ∈V(G))▒supp〖(v)〗 and it is denoted by supp(G). In this paper, open support of some graphs is studied.
Źródło:
World Scientific News; 2021, 156; 130-146
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vertex-disjoint stars in graphs
Autorzy:
Ota, Katsuhiro
Powiązania:
https://bibliotekanauki.pl/articles/743470.pdf
Data publikacji:
2001
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
stars
vertex-disjoint copies
minimum degree
Opis:
In this paper, we give a sufficient condition for a graph to contain vertex-disjoint stars of a given size. It is proved that if the minimum degree of the graph is at least k+t-1 and the order is at least (t+1)k + O(t²), then the graph contains k vertex-disjoint copies of a star $K_{1,t}$. The condition on the minimum degree is sharp, and there is an example showing that the term O(t²) for the number of uncovered vertices is necessary in a sense.
Źródło:
Discussiones Mathematicae Graph Theory; 2001, 21, 2; 179-185
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Rainbow Vertex-Connection
Autorzy:
Li, Xueliang
Shi, Yongtang
Powiązania:
https://bibliotekanauki.pl/articles/30146636.pdf
Data publikacji:
2013-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
rainbow vertex-connection
vertex coloring
minimum degree
2-step dominating set
Opis:
A vertex-colored graph is rainbow vertex-connected if any two vertices are connected by a path whose internal vertices have distinct colors. The rainbow vertex-connection of a connected graph $G$, denoted by $rvc(G)$, is the smallest number of colors that are needed in order to make $G$ rainbow vertex-connected. It was proved that if $G$ is a graph of order $n$ with minimum degree $ \delta $, then $ rvc(G) < 11n//\delta$. In this paper, we show that $rvc(G) \le 3n//(δ+1)+5$ for $ \delta \ge \sqrt{n-1} -1 $ and $ n \le 290 $, while $ rvc(G) \le 4n//(δ + 1) + 5 $ for $ 16 \le \delta \le \sqrt{n-1}-2 $ and $ rvc(G) \le 4n//(\delta + 1) + C(\delta) $ for $6 \le \delta \le 15$, where $ C(\delta) = e^\frac{ 3 \log (\delta^3 + 2 \delta^2 +3)-3(\log 3 - 1)}{\delta - 3} - 2$. We also prove that $ rvc(G) \le 3n//4 − 2 $ for $ \delta = 3$, $ rvc(G) \le 3n//5 − 8//5$ for $\delta = 4$ and $rvc(G) \le n//2 − 2$ for $\delta = 5$. Moreover, an example constructed by Caro et al. shows that when $ \delta \ge \sqrt{n-1} - 1 $ and $ \delta = 3, 4, 5 $, our bounds are seen to be tight up to additive constants.
Źródło:
Discussiones Mathematicae Graph Theory; 2013, 33, 2; 307-313
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vertex-disjoint copies of K¯₄
Autorzy:
Kawarabayashi, Ken-ichi
Powiązania:
https://bibliotekanauki.pl/articles/744487.pdf
Data publikacji:
2004
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
extremal graph theory
vertex disjoint copy
minimum degree
Opis:
Let G be a graph of order n. Let K¯ₗ be the graph obtained from Kₗ by removing one edge.
In this paper, we propose the following conjecture:
Let G be a graph of order n ≥ lk with δ(G) ≥ (n-k+1)(l-3)/(l-2)+k-1. Then G has k vertex-disjoint K¯ₗ.
This conjecture is motivated by Hajnal and Szemerédi's [6] famous theorem. In this paper, we verify this conjecture for l=4.
Źródło:
Discussiones Mathematicae Graph Theory; 2004, 24, 2; 249-262
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heavy cycles in weighted graphs
Autorzy:
Bondy, J.
Broersma, Hajo
van den Heuvel, Jan
Veldman, Henk
Powiązania:
https://bibliotekanauki.pl/articles/743527.pdf
Data publikacji:
2002
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
weighted graph
(long, optimal, Hamilton) cycle
(edge-, vertex-)weighting
weighted degree
Opis:
An (edge-)weighted graph is a graph in which each edge e is assigned a nonnegative real number w(e), called the weight of e. The weight of a cycle is the sum of the weights of its edges, and an optimal cycle is one of maximum weight. The weighted degree w(v) of a vertex v is the sum of the weights of the edges incident with v. The following weighted analogue (and generalization) of a well-known result by Dirac for unweighted graphs is due to Bondy and Fan. Let G be a 2-connected weighted graph such that w(v) ≥ r for every vertex v of G. Then either G contains a cycle of weight at least 2r or every optimal cycle of G is a Hamilton cycle. We prove the following weighted analogue of a generalization of Dirac's result that was first proved by Pósa. Let G be a 2-connected weighted graph such that w(u)+w(v) ≥ s for every pair of nonadjacent vertices u and v. Then G contains either a cycle of weight at least s or a Hamilton cycle. Examples show that the second conclusion cannot be replaced by the stronger second conclusion from the result of Bondy and Fan. However, we characterize a natural class of edge-weightings for which these two conclusions are equivalent, and show that such edge-weightings can be recognized in time linear in the number of edges.
Źródło:
Discussiones Mathematicae Graph Theory; 2002, 22, 1; 7-15
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the hat problem on a graph
Autorzy:
Krzywkowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/256048.pdf
Data publikacji:
2012
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
hat problem
graph
degree
neighborhood
neighborhood-dominated
unicyclic
universal vertex
Nordhaus-Gaddum
Opis:
The topic of this paper is the hat problem in which each of n players is uniformly and independently fitted with a blue or red hat. Then everybody can try to guess simultaneously his own hat color by looking at the hat colors of the other players. The team wins if at least one player guesses his hat color correctly, and no one guesses his hat color wrong; otherwise the team loses. The aim is to maximize the probability of winning. In this version every player can see everybody excluding himself. We consider such a problem on a graph, where vertices correspond to players, and a player can see each player to whom he is connected by an edge. The solution of the hat problem on a graph is known for trees and for cycles on four or at least nine vertices. In this paper first we give an upper bound on the maximum chance of success for graphs with neighborhood-dominated vertices. Next we solve the problem on unicyclic graphs containing a cycle on at least nine vertices. We prove that the maximum chance of success is one by two. Then we consider the hat problem on a graph with a universal vertex. We prove that there always exists an optimal strategy such that in every case some vertex guesses its color. Moreover, we prove that there exists a graph with a universal vertex for which there exists an optimal strategy such that in some case no vertex guesses its color. We also give some Nordhaus-Gaddum type inequalities.
Źródło:
Opuscula Mathematica; 2012, 32, 2; 285-296
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spectral Radius and Hamiltonicity of Graphs
Autorzy:
Yu, Guidong
Fang, Yi
Fan, Yizheng
Cai, Gaixiang
Powiązania:
https://bibliotekanauki.pl/articles/31343181.pdf
Data publikacji:
2019-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
spectral radius
singless Laplacian spectral radius
traceable
Hamiltonian-connected
traceable from every vertex
minimum degree
Opis:
In this paper, we study the Hamiltonicity of graphs with large minimum degree. Firstly, we present some conditions for a simple graph to be Hamilton-connected and traceable from every vertex in terms of the spectral radius of the graph or its complement, respectively. Secondly, we give the conditions for a nearly balanced bipartite graph to be traceable in terms of spectral radius, signless Laplacian spectral radius of the graph or its quasi-complement, respectively.
Źródło:
Discussiones Mathematicae Graph Theory; 2019, 39, 4; 951-974
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-13 z 13

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