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Wyświetlanie 1-15 z 399
Tytuł:
Magic and supermagic dense bipartite graphs
Autorzy:
Ivanco, Jaroslav
Powiązania:
https://bibliotekanauki.pl/articles/743476.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
magic graphs
supermagic graphs
bipartite graphs
Opis:
A graph is called magic (supermagic) if it admits a labelling of the edges by pairwise different (and consecutive) positive integers such that the sum of the labels of the edges incident with a vertex is independent of the particular vertex. In the paper we prove that any balanced bipartite graph with minimum degree greater than |V(G)|/4 ≥ 2 is magic. A similar result is presented for supermagic regular bipartite graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2007, 27, 3; 583-591
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On some variations of extremal graph problems
Autorzy:
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/972027.pdf
Data publikacji:
1997
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
hereditary properties of graphs
maximal graphs
extremal graphs
saturated graphs
Opis:
A set P of graphs is termed hereditary property if and only if it contains all subgraphs of any graph G belonging to P. A graph is said to be maximal with respect to a hereditary property P (shortly P-maximal) whenever it belongs to P and none of its proper supergraphs of the same order has the property P. A graph is P-extremal if it has a the maximum number of edges among all P-maximal graphs of given order. The number of its edges is denoted by ex(n, P). If the number of edges of a P-maximal graph is minimum, then the graph is called P-saturated and its number of edges is denoted by sat(n, P).
In this paper, we consider two famous problems of extremal graph theory. We shall translate them into the language of P-maximal graphs and utilize the properties of the lattice of all hereditary properties in order to establish some general bounds and particular results. Particularly, we shall investigate the behaviour of sat(n,P) and ex(n,P) in some interesting intervals of the mentioned lattice.
Źródło:
Discussiones Mathematicae Graph Theory; 1997, 17, 1; 67-76
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tetravalent arc-transitive graphs of order $3p^2$
Autorzy:
Ghasemi, Mohsen
Powiązania:
https://bibliotekanauki.pl/articles/31231999.pdf
Data publikacji:
2014-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
s-transitive graphs
symmetric graphs
Cayley graphs
Opis:
Let $s$ be a positive integer. A graph is s-transitive if its automorphism group is transitive on s-arcs but not on $(s + 1)$-arcs. Let $p$ be a prime. In this article a complete classification of tetravalent s-transitive graphs of order $3p^2$ is given.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 3; 567-575
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Generalized Hamming Graphs: Some New Results
Autorzy:
Bedrane, Amari
Abdelhafid, Berrachedi
Powiązania:
https://bibliotekanauki.pl/articles/31342286.pdf
Data publikacji:
2018-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
generalized median graphs
Hamming graphs
quasi-median graphs
quasi-Hilbertian graphs
Opis:
A projection of a vertex x of a graph G over a subset S of vertices is a vertex of S at minimal distance from x. The study of projections over quasi-intervals gives rise to a new characterization of quasi-median graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2018, 38, 3; 627-633
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Supermagic Generalized Double Graphs
Autorzy:
Ivančo, Jaroslav
Powiązania:
https://bibliotekanauki.pl/articles/31341097.pdf
Data publikacji:
2016-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
double graphs
supermagic graphs
degree-magic graphs
Opis:
A graph G is called supermagic if it admits a labelling of the edges by pairwise di erent consecutive integers such that the sum of the labels of the edges incident with a vertex is independent of the particular vertex. In this paper we will introduce some constructions of supermagic labellings of some graphs generalizing double graphs. Inter alia we show that the double graphs of regular Hamiltonian graphs and some circulant graphs are supermagic.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 1; 211-225
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Clique irreducibility of some iterative classes of graphs
Autorzy:
Aparna Lakshmanan, S.
Vijayakumar, A.
Powiązania:
https://bibliotekanauki.pl/articles/743328.pdf
Data publikacji:
2008
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
line graphs
Gallai graphs
anti-Gallai graphs
clique irreducible graphs
clique vertex irreducible graphs
Opis:
In this paper, two notions, the clique irreducibility and clique vertex irreducibility are discussed. A graph G is clique irreducible if every clique in G of size at least two, has an edge which does not lie in any other clique of G and it is clique vertex irreducible if every clique in G has a vertex which does not lie in any other clique of G. It is proved that L(G) is clique irreducible if and only if every triangle in G has a vertex of degree two. The conditions for the iterations of line graph, the Gallai graphs, the anti-Gallai graphs and its iterations to be clique irreducible and clique vertex irreducible are also obtained.
Źródło:
Discussiones Mathematicae Graph Theory; 2008, 28, 2; 307-321
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A characterization of complete tripartite degree-magic graphs
Autorzy:
Bezegová, Ľudmila
Ivančo, Jaroslav
Powiązania:
https://bibliotekanauki.pl/articles/743198.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
supermagic graphs
degree-magic graphs
complete tripartite graphs
Opis:
A graph is called degree-magic if it admits a labelling of the edges by integers 1, 2,..., |E(G)| such that the sum of the labels of the edges incident with any vertex v is equal to (1+ |E(G)|)/2*deg(v). Degree-magic graphs extend supermagic regular graphs. In this paper we characterize complete tripartite degree-magic graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2012, 32, 2; 243-253
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
How Long Can One Bluff in the Domination Game?
Autorzy:
Brešar, Boštan
Dorbec, Paul
Klavžar, Sandi
Košmrlj, Gašpar
Powiązania:
https://bibliotekanauki.pl/articles/31341979.pdf
Data publikacji:
2017-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination game
game domination number
bluff graphs
minus graphs
generalized Petersen graphs
Kneser graphs
Cartesian product of graphs
Hamming graphs
Opis:
The domination game is played on an arbitrary graph G by two players, Dominator and Staller. The game is called Game 1 when Dominator starts it, and Game 2 otherwise. In this paper bluff graphs are introduced as the graphs in which every vertex is an optimal start vertex in Game 1 as well as in Game 2. It is proved that every minus graph (a graph in which Game 2 finishes faster than Game 1) is a bluff graph. A non-trivial infinite family of minus (and hence bluff) graphs is established. minus graphs with game domination number equal to 3 are characterized. Double bluff graphs are also introduced and it is proved that Kneser graphs K(n, 2), n ≥ 6, are double bluff. The domination game is also studied on generalized Petersen graphs and on Hamming graphs. Several generalized Petersen graphs that are bluff graphs but not vertex-transitive are found. It is proved that Hamming graphs are not double bluff.
Źródło:
Discussiones Mathematicae Graph Theory; 2017, 37, 2; 337-352
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cyclability in bipartite graphs
Autorzy:
Amar, D.
Flandrin, E.
Gancarzewicz, G.
Powiązania:
https://bibliotekanauki.pl/articles/255877.pdf
Data publikacji:
2009
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
graphs
cycles
bipartite graphs
Opis:
Let G = (X, Y; E) be a balanced 2-connected bipartite graph and S ⊂ V(G). We will say that S is cyclable in G if all vertices of S belong to a common cycle in G. We give sufficient degree conditions in a balanced bipartite graph G and a subset S ⊂ V(G) for the cyclability of the set S.
Źródło:
Opuscula Mathematica; 2009, 29, 4; 345-364
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
2-splittable and cordial graphs
Autorzy:
Cichacz, S.
Powiązania:
https://bibliotekanauki.pl/articles/255946.pdf
Data publikacji:
2010
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
cordial graphs
2-splittable graphs
Opis:
E. Miller and G.E. Stevens proved in [5] the existence of certain families of 2-splittable caterpillars. In this paper we characterize other families of 2-splittable caterpillars. Moreover, we show that for some of them there exists a friendly labeling inducing two isomorphic subgraphs.
Źródło:
Opuscula Mathematica; 2010, 30, 1; 61-67
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A characterization of planar median graphs
Autorzy:
Peterin, Iztok
Powiązania:
https://bibliotekanauki.pl/articles/744189.pdf
Data publikacji:
2006
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
median graphs
planar graphs
expansion
Opis:
Median graphs have many interesting properties. One of them is-in connection with triangle free graphs-the recognition complexity. In general the complexity is not very fast, but if we restrict to the planar case the recognition complexity becomes linear. Despite this fact, there is no characterization of planar median graphs in the literature. Here an additional condition is introduced for the convex expansion procedure that characterizes planar median graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2006, 26, 1; 41-48
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The General Position Problem on Kneser Graphs and on Some Graph Operations
Autorzy:
Ghorbani, Modjtaba
Maimani, Hamid Reza
Momeni, Mostafa
Mahid, Farhad Rahimi
Klavžar, Sandi
Rus, Gregor
Powiązania:
https://bibliotekanauki.pl/articles/32222714.pdf
Data publikacji:
2021-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
general position set
Kneser graphs
Cartesian product of graphs
corona over graphs
line graphs
Opis:
A vertex subset S of a graph G is a general position set of G if no vertex of S lies on a geodesic between two other vertices of S. The cardinality of a largest general position set of G is the general position number (gp-number) gp(G) of G. The gp-number is determined for some families of Kneser graphs, in particular for K(n, 2), n ≥ 4, and K(n, 3), n ≥ 9. A sharp lower bound on the gp-number is proved for Cartesian products of graphs. The gp-number is also determined for joins of graphs, coronas over graphs, and line graphs of complete graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 4; 1199-1213
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On hereditary properties of composition graphs
Autorzy:
Levit, Vadim
Mandrescu, Eugen
Powiązania:
https://bibliotekanauki.pl/articles/744221.pdf
Data publikacji:
1998
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
composition graph
co-graphs
θ₁-perfect graphs
threshold graphs
Opis:
The composition graph of a family of n+1 disjoint graphs ${H_i:0 ≤ i ≤ n}$ is the graph H obtained by substituting the n vertices of H₀ respectively by the graphs H₁,H₂,...,Hₙ. If H has some hereditary property P, then necessarily all its factors enjoy the same property. For some sort of graphs it is sufficient that all factors ${H_i: 0 ≤ i ≤ n}$ have a certain common P to endow H with this P. For instance, it is known that the composition graph of a family of perfect graphs is also a perfect graph (B. Bollobas, 1978), and the composition graph of a family of comparability graphs is a comparability graph as well (M.C. Golumbic, 1980). In this paper we show that the composition graph of a family of co-graphs (i.e., P₄-free graphs), is also a co-graph, whereas for θ₁-perfect graphs (i.e., P₄-free and C₄-free graphs) and for threshold graphs (i.e., P₄-free, C₄-free and 2K₂-free graphs), the corresponding factors ${H_i:0 ≤ i ≤ n}$ have to be equipped with some special structure.
Źródło:
Discussiones Mathematicae Graph Theory; 1998, 18, 2; 183-195
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A note on a new condition implying pancyclism
Autorzy:
Flandrin, Evelyne
Li, Hao
Marczyk, Antoni
Woźniak, Mariusz
Powiązania:
https://bibliotekanauki.pl/articles/743445.pdf
Data publikacji:
2001
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
hamiltonian graphs
pancyclic graphs
cycles
Opis:
We first show that if a 2-connected graph G of order n is such that for each two vertices u and v such that δ = d(u) and d(v) < n/2 the edge uv belongs to E(G), then G is hamiltonian. Next, by using this result, we prove that a graph G satysfying the above condition is either pancyclic or isomorphic to $K_{n/2,n/2}$.
Źródło:
Discussiones Mathematicae Graph Theory; 2001, 21, 1; 137-143
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New sufficient conditions for hamiltonian and pancyclic graphs
Autorzy:
Schiermeyer, Ingo
Woźniak, Mariusz
Powiązania:
https://bibliotekanauki.pl/articles/743639.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
hamiltonian graphs
pancyclic graphs
closure
Opis:
For a graph G of order n we consider the unique partition of its vertex set V(G) = A ∪ B with A = {v ∈ V(G): d(v) ≥ n/2} and B = {v ∈ V(G):d(v) < n/2}. Imposing conditions on the vertices of the set B we obtain new sufficient conditions for hamiltonian and pancyclic graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2007, 27, 1; 29-38
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 399

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