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Wyświetlanie 1-15 z 15
Tytuł:
Trees with Distinguishing Index Equal Distinguishing Number Plus One
Autorzy:
Alikhani, Saeid
Klavžar, Sandi
Lehner, Florian
Soltani, Samaneh
Powiązania:
https://bibliotekanauki.pl/articles/31804165.pdf
Data publikacji:
2020-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
automorphism group
distinguishing index
distinguishing number
tree
unicyclic graph
Opis:
The distinguishing number (index) D(G) (D′ (G)) of a graph G is the least integer d such that G has an vertex (edge) labeling with d labels that is preserved only by the trivial automorphism. It is known that for every graph G we have D′ (G) ≤ D(G) + 1. In this note we characterize finite trees for which this inequality is sharp. We also show that if G is a connected unicyclic graph, then D′ (G) = D(G).
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 3; 875-884
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:
Total connected domination game
Autorzy:
Bujtás, Csilla
Henning, Michael A.
Iršič, Vesna
Klavžar, Sandi
Powiązania:
https://bibliotekanauki.pl/articles/2050904.pdf
Data publikacji:
2021
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
connected domination game
total connected domination game
graph product
tree
Opis:
The (total) connected domination game on a graph $G$ is played by two players, Dominator and Staller, according to the standard (total) domination game with the additional requirement that at each stage of the game the selected vertices induce a connected subgraph of $G$. If Dominator starts the game and both players play optimally, then the number of vertices selected during the game is the (total) connected game domination number $(\gamma_{tcg}(G))(\gamma_{cg(G)})$ of $G$. We show that $\gamma_{tcg}(G) \in \{\gamma_{cg}(G), \gamma_{cg}(G)+1, \gamma_{cg}(G)+2\}$, and consequently define $G$ as Class $i$ if $\gamma_{tcg}(G) = \gamma_{cg}(G)+i$ for $i \in \{0, 1, 2\}$. A large family of Class 0 graphs is constructed which contains all connected Cartesian product graphs and connected direct product graphs with minimum degree at least 2. We show that no tree is Class 2 and characterize Class 1 trees. We provide an infinite family of Class 2 bipartite graphs.
Źródło:
Opuscula Mathematica; 2021, 41, 4; 453-464
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
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:
Strong Geodetic Problem in Networks
Autorzy:
Manuel, Paul
Klavžar, Sandi
Xavier, Antony
Arokiaraj, Andrew
Thomas, Elizabeth
Powiązania:
https://bibliotekanauki.pl/articles/32083731.pdf
Data publikacji:
2020-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
geodetic problem
strong geodetic problem
Apollonian networks
Sierpiński graphs
computational complexity
Opis:
In order to model certain social network problems, the strong geodetic problem and its related invariant, the strong geodetic number, are introduced. The problem is conceptually similar to the classical geodetic problem but seems intrinsically more difficult. The strong geodetic number is compared with the geodetic number and with the isometric path number. It is determined for several families of graphs including Apollonian networks. Applying Sierpiński graphs, an algorithm is developed that returns a minimum path cover of Apollonian networks corresponding to the strong geodetic number. It is also proved that the strong geodetic problem is NP-complete.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 1; 307-321
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some results on total domination in direct products of graphs
Autorzy:
Dorbec, Paul
Gravier, Sylvain
Klavžar, Sandi
Spacapan, Simon
Powiązania:
https://bibliotekanauki.pl/articles/743885.pdf
Data publikacji:
2006
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
direct product
total domination
k-tuple domination
open packing
domination
Opis:
Upper and lower bounds on the total domination number of the direct product of graphs are given. The bounds involve the {2}-total domination number, the total 2-tuple domination number, and the open packing number of the factors. Using these relationships one exact total domination number is obtained. An infinite family of graphs is constructed showing that the bounds are best possible. The domination number of direct products of graphs is also bounded from below.
Źródło:
Discussiones Mathematicae Graph Theory; 2006, 26, 1; 103-112
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:
On the rainbow connection of Cartesian products and their subgraphs
Autorzy:
Klavžar, Sandi
Mekiš, Gašper
Powiązania:
https://bibliotekanauki.pl/articles/743307.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
rainbow connection
strong rainbow connection
Cartesian product of graphs
isometric subgraph
hypercube
Opis:
Rainbow connection number of Cartesian products and their subgraphs are considered. Previously known bounds are compared and non-existence of such bounds for subgraphs of products are discussed. It is shown that the rainbow connection number of an isometric subgraph of a hypercube is bounded above by the rainbow connection number of the hypercube. Isometric subgraphs of hypercubes with the rainbow connection number as small as possible compared to the rainbow connection of the hypercube are constructed. The concept of c-strong rainbow connected coloring is introduced. In particular, it is proved that the so-called Θ-coloring of an isometric subgraph of a hypercube is its unique optimal c-strong rainbow connected coloring.
Źródło:
Discussiones Mathematicae Graph Theory; 2012, 32, 4; 783-793
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Grundy Total Domination Number in Product Graphs
Autorzy:
Brešar, Boštjan
Bujtás, Csilla
Gologranc, Tanja
Klavžar, Sandi
Košmrlj, Gašper
Marc, Tilen
Patkós, Balázs
Tuza, Zsolt
Vizer, Máté
Powiązania:
https://bibliotekanauki.pl/articles/32083828.pdf
Data publikacji:
2021-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
total domination
Grundy total domination number
graph product
Opis:
A longest sequence $(v_1, . . ., v_k)$ of vertices of a graph $G$ is a Grundy total dominating sequence of $G$ if for all $i$, \(N(υ_i)\backslash\bigcup_{j=1}^{i-1}N(υ_j)≠∅\). The length $k$ of the sequence is called the Grundy total domination number of $G$ and denoted $\gamma_{gr}^t(G)$. In this paper, the Grundy total domination number is studied on four standard graph products. For the direct product we show that $\gamma_{gr}^t(G×H)≥\gamma_{gr}^t(G)\gamma_{gr}^t(H)$, conjecture that the equality always holds, and prove the conjecture in several special cases. For the lexicographic product we express $\gamma_{gr}^t(G∘H)$ in terms of related invariant of the factors and find some explicit formulas for it. For the strong product, lower bounds on $\gamma_{gr}^t(G⊠H)$ are proved as well as upper bounds for products of paths and cycles. For the Cartesian product we prove lower and upper bounds on the Grundy total domination number when factors are paths or cycles.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 1; 225-247
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:
Isomorphic components of Kronecker product of bipartite graphs
Autorzy:
Jha, Pranava
Klavžar, Sandi
Zmazek, Blaž
Powiązania:
https://bibliotekanauki.pl/articles/971945.pdf
Data publikacji:
1997
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Kronecker product
bipartite graphs
graph isomorphism
Opis:
Weichsel (Proc. Amer. Math. Soc. 13 (1962) 47-52) proved that the Kronecker product of two connected bipartite graphs consists of two connected components. A condition on the factor graphs is presented which ensures that such components are isomorphic. It is demonstrated that several familiar and easily constructible graphs are amenable to that condition. A partial converse is proved for the above condition and it is conjectured that the converse is true in general.
Źródło:
Discussiones Mathematicae Graph Theory; 1997, 17, 2; 301-309
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:
Edge-Transitive Lexicographic and Cartesian Products
Autorzy:
Imrich, Wilfried
Iranmanesh, Ali
Klavžar, Sandi
Soltani, Abolghasem
Powiązania:
https://bibliotekanauki.pl/articles/31340755.pdf
Data publikacji:
2016-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge-transitive graph
vertex-transitive graph
lexicographic product of graphs
Cartesian product of graphs
Opis:
In this note connected, edge-transitive lexicographic and Cartesian products are characterized. For the lexicographic product G ◦ H of a connected graph G that is not complete by a graph H, we show that it is edge-transitive if and only if G is edge-transitive and H is edgeless. If the first factor of G ∘ H is non-trivial and complete, then G ∘ H is edge-transitive if and only if H is the lexicographic product of a complete graph by an edgeless graph. This fixes an error of Li, Wang, Xu, and Zhao [11]. For the Cartesian product it is shown that every connected Cartesian product of at least two non-trivial factors is edge-transitive if and only if it is the Cartesian power of a connected, edge- and vertex-transitive graph.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 4; 857-865
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Domination Game Critical Graphs
Autorzy:
Bujtás, Csilla
Klavžar, Sandi
Košmrlj, Gašper
Powiązania:
https://bibliotekanauki.pl/articles/31234048.pdf
Data publikacji:
2015-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination number
domination game
domination game critical graphs
powers of cycles
trees
Opis:
The domination game is played on a graph $G$ by two players who alternately take turns by choosing a vertex such that in each turn at least one previously undominated vertex is dominated. The game is over when each vertex becomes dominated. One of the players, namely Dominator, wants to finish the game as soon as possible, while the other one wants to delay the end. The number of turns when Dominator starts the game on $G$ and both players play optimally is the graph invariant $ \gamma_g (G) $, named the game domination number. Here we study the $ \gamma_g$-critical graphs which are critical with respect to vertex predomination. Besides proving some general properties, we characterize $ \gamma_g$-critical graphs with $ \gamma_g = 2$ and with $ \gamma_g = 3$, moreover for each n we identify the (infinite) class of all $\gamma_g$-critical ones among the $n$th powers $ C_N^n$ of cycles. Along the way we determine $\gamma_{g} ( C_N^n ) $ for all $n$ and $N$. Results of a computer search for $ \gamma_g$-critical trees are presented and several problems and research directions are also listed.
Źródło:
Discussiones Mathematicae Graph Theory; 2015, 35, 4; 781-796
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Survey on Packing Colorings
Autorzy:
Brešar, Boštjan
Ferme, Jasmina
Klavžar, Sandi
Rall, Douglas F.
Powiązania:
https://bibliotekanauki.pl/articles/31804166.pdf
Data publikacji:
2020-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
packing coloring
packing chromatic number
subcubic graph
S -packing chromatic number
computational complexity
Opis:
If S = (a1, a2, . . .) is a non-decreasing sequence of positive integers, then an S-packing coloring of a graph G is a partition of V (G) into sets X1, X2, . . . such that for each pair of distinct vertices in the set Xi, the distance between them is larger than ai. If there exists an integer k such that V (G) = X1 ∪ ∪ Xk, then the partition is called an S-packing k-coloring. The S-packing chromatic number of G is the smallest k such that G admits an S-packing k-coloring. If ai = i for every i, then the terminology reduces to packing colorings and packing chromatic number. Since the introduction of these generalizations of the chromatic number in 2008 more than fifty papers followed. Here we survey the state of the art on the packing coloring, and its generalization, the S-packing coloring. We also list several conjectures and open problems.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 4; 923-970
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-15 z 15

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