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Tytuł:
Maximum Edge-Colorings Of Graphs
Autorzy:
Jendrol’, Stanislav
Vrbjarová, Michaela
Powiązania:
https://bibliotekanauki.pl/articles/31341153.pdf
Data publikacji:
2016-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge-coloring
r -maximum k -edge-coloring
unique-maximum edge-coloring
weak-odd edge-coloring
weak-even edge-coloring
Opis:
An $r$-maximum $k$-edge-coloring of $G$ is a $k$-edge-coloring of $G$ having a property that for every vertex $v$ of degree $d_G(v) = d, d \ge r$, the maximum color, that is present at vertex $v$, occurs at $v$ exactly $r$ times. The $r$-maximum index $ \chi_r^′ (G) $ is defined to be the minimum number $k$ of colors needed for an $r$-maximum $k$-edge-coloring of graph $G$. In this paper we show that $ \chi_r^′ (G) \le 3 $ for any nontrivial connected graph $G$ and $ r = 1$ or 2. The bound 3 is tight. All graphs $G$ with $ \chi_1^' (G) =i $, $i = 1, 2, 3$ are characterized. The precise value of the $r$-maximum index, $ r \ge 1 $, is determined for trees and complete graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 1; 117-125
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
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:
The upper edge geodetic number and the forcing edge geodetic number of a graph
Autorzy:
Santhakumaran, A. P.
John, J.
Powiązania:
https://bibliotekanauki.pl/articles/255845.pdf
Data publikacji:
2009
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
geodetic number
edge geodetic basis
edge geodetic number
upper edge geodetic number
forcing edge geodetic number
Opis:
An edge geodetic set of a connected graph G of order p ≥ 2 is a set S ⊆ V(G) such that every edge of G is contained in a geodesic joining some pair of vertices in S. The edge geodetic number g1(G) of G is the minimum cardinality of its edge geodetic sets and any edge geodetic set of cardinality g1(G) is a minimum edge geodetic set of G or an edge geodetic basis of G. An edge geodetic set S in a connected graph G is a minimal edge geodetic set if no proper subset of S is an edge geodetic set of G. The upper edge geodetic number g1+(G) of G is the maximum cardinality of a minimal edge geodetic set of G. The upper edge geodetic number of certain classes of graphs are determined. It is shown that for every two integers a and b such that 2 ≤ a ≤ b, there exists a connected graph G with g1(G) = a and g1+(G) = b. For an edge geodetic basis S of G, a subset T ⊆ S is called a forcing subset for S if S is the unique edge geodetic basis containing T. A forcing subset for S of minimum cardinality is a minimum forcing subset of S. The forcing edge geodetic number of S denoted by ƒ1(S), is the cardinality of a minimum forcing subset of S. The forcing edge geodetic number of G, denoted by ƒ1(G), is ƒ1(G) = min{ ƒ1(S)}, where the minimum is taken over all edge geodetic bases S in G. Some general properties satisfied by this concept are studied. The forcing edge geodetic number of certain classes of graphs are determined. It is shown that for every pair a, b of integers with 0 ≤ a < b and b ≥ 2, there exists a connected graph G such thatƒ1(G) = a and g1(G) = b.
Źródło:
Opuscula Mathematica; 2009, 29, 4; 427-441
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On edge detour graphs
Autorzy:
Santhakumaran, A.P.
Athisayanathan, S.
Powiązania:
https://bibliotekanauki.pl/articles/744551.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
detour
edge detour set
edge detour basis
edge detour number
Opis:
For two vertices u and v in a graph G = (V,E), the detour distance D(u,v) is the length of a longest u-v path in G. A u-v path of length D(u,v) is called a u-v detour. A set S ⊆V is called an edge detour set if every edge in G lies on a detour joining a pair of vertices of S. The edge detour number dn₁(G) of G is the minimum order of its edge detour sets and any edge detour set of order dn₁(G) is an edge detour basis of G. A connected graph G is called an edge detour graph if it has an edge detour set. It is proved that for any non-trivial tree T of order p and detour diameter D, dn₁(T) ≤ p-D+1 and dn₁(T) = p-D+1 if and only if T is a caterpillar. We show that for each triple D, k, p of integers with 3 ≤ k ≤ p-D+1 and D ≥ 4, there is an edge detour graph G of order p with detour diameter D and dn₁(G) = k. We also show that for any three positive integers R, D, k with k ≥ 3 and R < D ≤ 2R, there is an edge detour graph G with detour radius R, detour diameter D and dn₁(G) = k. Edge detour graphs G with detour diameter D ≤ 4 are characterized when dn₁(G) = p-2 or dn₁(G) = p-1.
Źródło:
Discussiones Mathematicae Graph Theory; 2010, 30, 1; 155-174
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sufficient Conditions for Maximally Edge-Connected and Super-Edge-Connected Graphs Depending on The Clique Number
Autorzy:
Volkmann, Lutz
Powiązania:
https://bibliotekanauki.pl/articles/31343389.pdf
Data publikacji:
2019-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge-connectivity
clique number
maximally edge-connected graphs
super-edge-connected graphs
Opis:
Let G be a connected graph with minimum degree δ and edge-connectivity λ. A graph is maximally edge-connected if λ = δ, and it is super-edgeconnected if every minimum edge-cut is trivial; that is, if every minimum edge-cut consists of edges incident with a vertex of minimum degree. The clique number ω(G) of a graph G is the maximum cardinality of a complete subgraph of G. In this paper, we show that a connected graph G with clique number ω(G) ≤ r is maximally edge-connected or super-edge-connected if the number of edges is large enough. These are generalizations of corresponding results for triangle-free graphs by Volkmann and Hong in 2017.
Źródło:
Discussiones Mathematicae Graph Theory; 2019, 39, 2; 567-573
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The edge geodetic number and Cartesian product of graphs
Autorzy:
Santhakumaran, A.
Ullas Chandran, S.
Powiązania:
https://bibliotekanauki.pl/articles/744517.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
geodetic number
edge geodetic number
linear edge geodetic set
perfect edge geodetic set
(edge, vertex)-geodetic set
superior edge geodetic set
Opis:
For a nontrivial connected graph G = (V(G),E(G)), a set S⊆ V(G) is called an edge geodetic set of G if every edge of G is contained in a geodesic joining some pair of vertices in S. The edge geodetic number g₁(G) of G is the minimum order of its edge geodetic sets. Bounds for the edge geodetic number of Cartesian product graphs are proved and improved upper bounds are determined for a special class of graphs. Exact values of the edge geodetic number of Cartesian product are obtained for several classes of graphs. Also we obtain a necessary condition of G for which g₁(G ☐ K₂) = g₁(G).
Źródło:
Discussiones Mathematicae Graph Theory; 2010, 30, 1; 55-73
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the independence number of edge chromatic critical graphs
Autorzy:
Pang, Shiyou
Miao, Lianying
Song, Wenyao
Miao, Zhengke
Powiązania:
https://bibliotekanauki.pl/articles/30148675.pdf
Data publikacji:
2014-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge coloring
edge-chromatic critical graphs
independence number
Opis:
In 1968, Vizing conjectured that for any edge chromatic critical graph $G = (V,E)$ with maximum degree $△$ and independence number $α(G)$, $α(G) ≤ \frac{|V|}{2}$. It is known that $α(G) < \frac{3∆−2}{5∆−2}|V|$. In this paper we improve this bound when $△≥4$. Our precise result depends on the number $n_2$ of 2-vertices in $G$, but in particular we prove that $α(G) ≤\frac{3∆−3}{5∆−3}|V|$ when $△≥5$ and $n_2≤2(△− 1)$.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 3; 577-584
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the ρ-Edge Stability Number of Graphs
Autorzy:
Kemnitz, Arnfried
Marangio, Massimiliano
Powiązania:
https://bibliotekanauki.pl/articles/32361738.pdf
Data publikacji:
2022-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge stability number
line stability
invariant
chromatic edge stability index
chromatic index
edge coloring
Opis:
For an arbitrary invariant $ \rho(G) $ of a graph $G$ the $ \rho $-edge stability number $ es_\rho (G) $ is the minimum number of edges of $G$ whose removal results in a graph $ H \subseteq G $ with $ \rho (H) \ne \rho (G) $ or with $ E(H) = \emptyset $. In the first part of this paper we give some general lower and upper bounds for the $ \rho $-edge stability number. In the second part we study the $ \chi^' $-edge stability number of graphs, where $ \chi^' = \chi^' (G) $ is the chromatic index of $G$. We prove some general results for the so-called chromatic edge stability index $ es_{ \chi^′ } (G) $ and determine $ es_{ \chi^′ } (G) $ exactly for specific classes of graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 1; 249-262
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:
A note on M2-edge colorings of graphs
Autorzy:
Czap, J.
Powiązania:
https://bibliotekanauki.pl/articles/255532.pdf
Data publikacji:
2015
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
edge colouring
graph
Opis:
An edge coloring φ of a graph G is called an M2-edge coloring if [formula] every vertex v of G, where φ(v) is the set of colors of edges incident with v. Let K2(G) denote the maximum number of colors used in an M2-edge coloring of G. Let G1, G2 and G3 be graphs such that G1 ⊆ G2 ⊆ G3. In this paper we deal with the following question: Assuming that K2(G1) = K2(G3), does it hold K2(G1) = K2(G2) = K2(G3)?
Źródło:
Opuscula Mathematica; 2015, 35, 3; 287-291
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Decomposition of multigraphs
Autorzy:
Kouider, Mekkia
Mahéo, Maryvonne
Bryś, Krzysztof
Lonc, Zbigniew
Powiązania:
https://bibliotekanauki.pl/articles/744229.pdf
Data publikacji:
1998
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge decomposition
multigraph
Opis:
In this note, we consider the problem of existence of an edge-decomposition of a multigraph into isomorphic copies of 2-edge paths $K_{1,2}$. We find necessary and sufficient conditions for such a decomposition of a multigraph H to exist when
(i) either H does not have incident multiple edges or
(ii) multiplicities of the edges in H are not greater than two. In particular, we answer a problem stated by Z. Skupień.
Źródło:
Discussiones Mathematicae Graph Theory; 1998, 18, 2; 225-232
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
List Edge Coloring of Planar Graphs without 6-Cycles with Two Chords
Autorzy:
Hu, Linna
Sun, Lei
Wu, Jian-Liang
Powiązania:
https://bibliotekanauki.pl/articles/32083824.pdf
Data publikacji:
2021-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
planar graph
edge choosable
list edge chromatic number
chord
Opis:
A graph G is edge-L-colorable if for a given edge assignment L = {L(e) : e ∈ E(G)}, there exists a proper edge-coloring φ of G such that φ(e) ∈ L(e) for all e ∈ E(G). If G is edge-L-colorable for every edge assignment L such that |L(e)| ≥ k for all e ∈ E(G), then G is said to be edge-k-choosable. In this paper, we prove that if G is a planar graph without 6-cycles with two chords, then G is edge-k-choosable, where k = max{7, Δ(G) + 1}, and is edge-t-choosable, where t = max{9, Δ(G)}.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 1; 199-211
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Decompositions of multigraphs into parts with the same size
Autorzy:
Ivanco, Jaroslav
Powiązania:
https://bibliotekanauki.pl/articles/744275.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge decompositions
multigraphs
Opis:
Given a family ℱ of multigraphs without isolated vertices, a multigraph M is called ℱ-decomposable if M is an edge disjoint union of multigraphs each of which is isomorphic to a member of ℱ. We present necessary and sufficient conditions for existence of such decompositions if ℱ consists of all multigraphs of size q except for one. Namely, for a multigraph H of size q we find each multigraph M of size kq, such that every partition of the edge set of M into parts of cardinality q contains a part which induces a submultigraph of M isomorphic to H.
Źródło:
Discussiones Mathematicae Graph Theory; 2010, 30, 2; 335-347
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Minimum Edge Cuts in Diameter 2 Graphs
Autorzy:
Bickle, Allan
Schwenk, Allen
Powiązania:
https://bibliotekanauki.pl/articles/31343375.pdf
Data publikacji:
2019-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge connectivity
diameter
Opis:
Plesnik proved that the edge connectivity and minimum degree are equal for diameter 2 graphs. We provide a streamlined proof of this fact and characterize the diameter 2 graphs with a nontrivial minimum edge cut.
Źródło:
Discussiones Mathematicae Graph Theory; 2019, 39, 2; 605-608
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conflict-Free Connections of Graphs
Autorzy:
Czap, Július
Jendroľ, Stanislav
Valiska, Juraj
Powiązania:
https://bibliotekanauki.pl/articles/31342254.pdf
Data publikacji:
2018-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge-coloring
conflict-free connection
2-edge-connected graph
tree
Opis:
An edge-colored graph G is conflict-free connected if any two of its vertices are connected by a path, which contains a color used on exactly one of its edges. In this paper the question for the smallest number of colors needed for a coloring of edges of G in order to make it conflict-free connected is investigated. We show that the answer is easy for 2-edge-connected graphs and very difficult for other connected graphs, including trees.
Źródło:
Discussiones Mathematicae Graph Theory; 2018, 38, 4; 911-920
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 373

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