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Wyświetlanie 1-11 z 11
Tytuł:
Median of a graph with respect to edges
Autorzy:
Santhakumaran, A.
Powiązania:
https://bibliotekanauki.pl/articles/743645.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
median
vertex-to-edge median
edge-to-vertex median
edge-to-edge median
Opis:
For any vertex v and any edge e in a non-trivial connected graph G, the distance sum d(v) of v is $d(v) = ∑_{u ∈ V}d(v,u)$, the vertex-to-edge distance sum d₁(v) of v is $d₁(v) = ∑_{e ∈ E}d(v,e)$, the edge-to-vertex distance sum d₂(e) of e is $d₂(e) = ∑_{v ∈ V}d(e,v)$ and the edge-to-edge distance sum d₃(e) of e is $d₃(e) = ∑_{f ∈ E}d(e,f)$. The set M(G) of all vertices v for which d(v) is minimum is the median of G; the set M₁(G) of all vertices v for which d₁(v) is minimum is the vertex-to-edge median of G; the set M₂(G) of all edges e for which d₂(e) is minimum is the edge-to-vertex median of G; and the set M₃(G) of all edges e for which d₃(e) is minimum is the edge-to-edge median of G. We determine these medians for some classes of graphs. We prove that the edge-to-edge median of a graph is the same as the median of its line graph. It is shown that the center and the median; the vertex-to-edge center and the vertex-to-edge median; the edge-to-vertex center and the edge-to-vertex median; and the edge-to-edge center and the edge-to-edge median of a graph are not only different but can be arbitrarily far apart.
Źródło:
Discussiones Mathematicae Graph Theory; 2012, 32, 1; 19-29
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Median and quasi-median direct products of graphs
Autorzy:
Brešar, Boštjan
Jha, Pranava
Klavžar, Sandi
Zmazek, Blaž
Powiązania:
https://bibliotekanauki.pl/articles/744332.pdf
Data publikacji:
2005
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
median graph
direct product
quasi-median graph
isometric embeddings
convexity
Opis:
Median graphs are characterized among direct products of graphs on at least three vertices. Beside some trivial cases, it is shown that one component of G×P₃ is median if and only if G is a tree in that the distance between any two vertices of degree at least 3 is even. In addition, some partial results considering median graphs of the form G×K₂ are proved, and it is shown that the only nonbipartite quasi-median direct product is K₃×K₃.
Źródło:
Discussiones Mathematicae Graph Theory; 2005, 25, 1-2; 183-196
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:
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 Median Problem on k-Partite Graphs
Autorzy:
Pravas, Karuvachery
Vijayakumar, Ambat
Powiązania:
https://bibliotekanauki.pl/articles/31339417.pdf
Data publikacji:
2015-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
networks
distance
median
bipartite
k-partite
Opis:
In a connected graph G, the status of a vertex is the sum of the distances of that vertex to each of the other vertices in G. The subgraph induced by the vertices of minimum (maximum) status in G is called the median (anti-median) of G. The median problem of graphs is closely related to the optimization problems involving the placement of network servers, the core of the entire networks. Bipartite graphs play a significant role in designing very large interconnection networks. In this paper, we answer a problem on the structure of medians of bipartite graphs by showing that any bipartite graph is the median (or anti-median) of another bipartite graph. Also, with a different construction, we show that the similar results hold for k-partite graphs, k ≥ 3. In addition, we provide constructions to embed another graph as center in both bipartite and k-partite cases. Since any graph is a k-partite graph, for some k, these constructions can be applied in general
Źródło:
Discussiones Mathematicae Graph Theory; 2015, 35, 3; 439-446
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modular and median signpost systems and their underlying graphs
Autorzy:
Mulder, Henry
Nebeský, Ladislav
Powiązania:
https://bibliotekanauki.pl/articles/743171.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
signpost system
modular graph
median graph
Opis:
The concept of a signpost system on a set is introduced. It is a ternary relation on the set satisfying three fairly natural axioms. Its underlying graph is introduced. When the underlying graph is disconnected some unexpected things may happen. The main focus are signpost systems satisfying some extra axioms. Their underlying graphs have lots of structure: the components are modular graphs or median graphs. Yet another axiom guarantees that the underlying graph is also connected. The main results of this paper concern if-and-only-if characterizations involving signpost systems satisfying additional axioms on the one hand and modular, respectively median graphs on the other hand.
Źródło:
Discussiones Mathematicae Graph Theory; 2003, 23, 2; 309-324
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Arboreal structure and regular graphs of median-like classes
Autorzy:
Brešar, Bostjan
Powiązania:
https://bibliotekanauki.pl/articles/743403.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
median graph
tree
gatedness
amalgam
periphery
regular graph
Opis:
We consider classes of graphs that enjoy the following properties: they are closed for gated subgraphs, gated amalgamation and Cartesian products, and for any gated subgraph the inverse of the gate function maps vertices to gated subsets. We prove that any graph of such a class contains a peripheral subgraph which is a Cartesian product of two graphs: a gated subgraph of the graph and a prime graph minus a vertex. Therefore, these graphs admit a peripheral elimination procedure which is a generalization of analogous procedure in median graphs. We characterize regular graphs of these classes whenever they enjoy an additional property. As a corollary we derive that regular weakly median graphs are precisely Cartesian products in which each factor is a complete graph or a hyperoctahedron.
Źródło:
Discussiones Mathematicae Graph Theory; 2003, 23, 2; 215-225
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The periphery graph of a median graph
Autorzy:
Brešar, Boštjan
Changat, Manoj
Subhamathi, Ajitha
Tepeh, Aleksandra
Powiązania:
https://bibliotekanauki.pl/articles/744496.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
median graph
Cartesian product
geodesic
periphery
peripheral expansion
Opis:
The periphery graph of a median graph is the intersection graph of its peripheral subgraphs. We show that every graph without a universal vertex can be realized as the periphery graph of a median graph. We characterize those median graphs whose periphery graph is the join of two graphs and show that they are precisely Cartesian products of median graphs. Path-like median graphs are introduced as the graphs whose periphery graph has independence number 2, and it is proved that there are path-like median graphs with arbitrarily large geodetic number. Peripheral expansion with respect to periphery graph is also considered, and connections with the concept of crossing graph are established.
Źródło:
Discussiones Mathematicae Graph Theory; 2010, 30, 1; 17-32
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On θ-graphs of partial cubes
Autorzy:
Klavžar, Sandi
Kovse, Matjaz
Powiązania:
https://bibliotekanauki.pl/articles/743784.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
intersection graph
partial cube
median graph
expansion theorem
Cartesian product of graphs
Opis:
The Θ-graph Θ(G) of a partial cube G is the intersection graph of the equivalence classes of the Djoković-Winkler relation. Θ-graphs that are 2-connected, trees, or complete graphs are characterized. In particular, Θ(G) is complete if and only if G can be obtained from K₁ by a sequence of (newly introduced) dense expansions. Θ-graphs are also compared with familiar concepts of crossing graphs and τ-graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2007, 27, 2; 313-321
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tree-like isometric subgraphs of hypercubes
Autorzy:
Brešar, Bostjan
Imrich, Wilfried
Klavžar, Sandi
Powiązania:
https://bibliotekanauki.pl/articles/743405.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
isometric embeddings
partial cubes
expansion procedures
trees
median graphs
graph automorphisms
automorphism groups
dismantlable graphs
Opis:
Tree-like isometric subgraphs of hypercubes, or tree-like partial cubes as we shall call them, are a generalization of median graphs. Just as median graphs they capture numerous properties of trees, but may contain larger classes of graphs that may be easier to recognize than the class of median graphs. We investigate the structure of tree-like partial cubes, characterize them, and provide examples of similarities with trees and median graphs. For instance, we show that the cube graph of a tree-like partial cube is dismantlable. This in particular implies that every tree-like partial cube G contains a cube that is invariant under every automorphism of G. We also show that weak retractions preserve tree-like partial cubes, which in turn implies that every contraction of a tree-like partial cube fixes a cube. The paper ends with several Frucht-type results and a list of open problems.
Źródło:
Discussiones Mathematicae Graph Theory; 2003, 23, 2; 227-240
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some properties of the zero divisor graph of a commutative ring
Autorzy:
Nazzal, Khalida
Ghanem, Manal
Powiązania:
https://bibliotekanauki.pl/articles/729189.pdf
Data publikacji:
2014
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
automorphism group of a graph
center of a graph
core of a graph
k-domination number
Gaussian integers modulo n
median of a graph
2-packing
perfect graph
and zero divisor graph
Opis:
Let Γ(R) be the zero divisor graph for a commutative ring with identity. The k-domination number and the 2-packing number of Γ(R), where R is an Artinian ring, are computed. k-dominating sets and 2-packing sets for the zero divisor graph of the ring of Gaussian integers modulo n, Γ(ℤₙ[i]), are constructed. The center, the median, the core, as well as the automorphism group of Γ(ℤₙ[i]) are determined. Perfect zero divisor graphs Γ(R) are investigated.
Źródło:
Discussiones Mathematicae - General Algebra and Applications; 2014, 34, 2; 167-181
1509-9415
Pojawia się w:
Discussiones Mathematicae - General Algebra and Applications
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-11 z 11

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