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Wyświetlanie 1-8 z 8
Tytuł:
Antipodal Edge-Colorings of Hypercubes
Autorzy:
West, Douglas B.
Wise, Jennifer I.
Powiązania:
https://bibliotekanauki.pl/articles/31343560.pdf
Data publikacji:
2019-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
antipodal edge-coloring
hypercube
monochromatic geodesic
Opis:
Two vertices of the k-dimensional hypercube Qk are antipodal if they differ in every coordinate. Edges uv and xy are antipodal if u is antipodal to x and v is antipodal to y. An antipodal edge-coloring of Qk is a 2- edge-coloring such that antipodal edges always have different colors. Norine conjectured that for k ≥ 2, in every antipodal edge-coloring of Qk some two antipodal vertices are connected by a monochromatic path. Feder and Subi proved this for k ≤ 5. We prove it for k ≤ 6.
Źródło:
Discussiones Mathematicae Graph Theory; 2019, 39, 1; 271-284
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Well-Covered Direct Products
Autorzy:
Kuenzel, Kirsti
Rall, Douglas F.
Powiązania:
https://bibliotekanauki.pl/articles/32315158.pdf
Data publikacji:
2022-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
well-covered graph
direct product of graphs
isolatable vertex
Opis:
A graph G is well-covered if all maximal independent sets of G have the same cardinality. In 1992 Topp and Volkmann investigated the structure of well-covered graphs that have nontrivial factorizations with respect to some of the standard graph products. In particular, they showed that both factors of a well-covered direct product are also well-covered and proved that the direct product of two complete graphs (respectively, two cycles) is well-covered precisely when they have the same order (respectively, both have order 3 or 4). Furthermore, they proved that the direct product of two well-covered graphs with independence number one-half their order is well-covered. We initiate a characterization of nontrivial connected well-covered graphs G and H, whose independence numbers are strictly less than one-half their orders, such that their direct product G × H is well-covered. In particular, we show that in this case both G and H have girth 3 and we present several infinite families of such well-covered direct products. Moreover, we show that if G is a factor of any well-covered direct product, then G is a complete graph unless it is possible to create an isolated vertex by removing the closed neighborhood of some independent set of vertices in G.
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 2; 627-640
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Graphs with Disjoint Dominating and 2-Dominating Sets
Autorzy:
Henning, Michael A.
Rall, Douglas F.
Powiązania:
https://bibliotekanauki.pl/articles/30146715.pdf
Data publikacji:
2013-03-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination
2-domination
vertex partition
Opis:
A DD2-pair of a graph G is a pair (D,D2) of disjoint sets of vertices of G such that D is a dominating set and D2 is a 2-dominating set of G. Although there are infinitely many graphs that do not contain a DD2-pair, we show that every graph with minimum degree at least two has a DD2-pair. We provide a constructive characterization of trees that have a DD2-pair and show that K3,3 is the only connected graph with minimum degree at least three for which D ∪ D2 necessarily contains all vertices of the graph.
Źródło:
Discussiones Mathematicae Graph Theory; 2013, 33, 1; 139-146
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A New Proof that 4-Connected Planar Graphs are Hamiltonian-Connected
Autorzy:
Lu, Xiaoyun
West, Douglas B.
Powiązania:
https://bibliotekanauki.pl/articles/31340879.pdf
Data publikacji:
2016-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
4-connected planar graph
Hamiltonian-connected
Tutte-path
Opis:
We prove a theorem guaranteeing special paths of faces in 2-connected plane graphs. As a corollary, we obtain a new proof of Thomassen’s theorem that every 4-connected planar graph is Hamiltonian-connected.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 3; 555-564
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Protection of Lexicographic Product Graphs
Autorzy:
Klein, Douglas J.
Rodríguez-Velázquez, Juan A.
Powiązania:
https://bibliotekanauki.pl/articles/32361746.pdf
Data publikacji:
2022-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
lexicographic product
weak Roman domination
secure domination
total domination
double total domination
Opis:
In this paper, we study the weak Roman domination number and the secure domination number of lexicographic product graphs. In particular, we show that these two parameters coincide for almost all lexicographic product graphs. Furthermore, we obtain tight bounds and closed formulas for these parameters.
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 1; 139-158
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
Tytuł:
The 1,2,3-Conjecture and 1,2-Conjecture for sparse graphs
Autorzy:
Cranston, Daniel W.
Jahanbekam, Sogol
West, Douglas B.
Powiązania:
https://bibliotekanauki.pl/articles/30148718.pdf
Data publikacji:
2014-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
reducible configuration
discharging method
1, 2, 3-Conjecture
1, 2-Conjecture
Opis:
The 1, 2, 3-Conjecture states that the edges of a graph without isolated edges can be labeled from {1, 2, 3} so that the sums of labels at adjacent vertices are distinct. The 1, 2-Conjecture states that if vertices also receive labels and the vertex label is added to the sum of its incident edge labels, then adjacent vertices can be distinguished using only {1, 2}. We show that various configurations cannot occur in minimal counterexamples to these conjectures. Discharging then confirms the conjectures for graphs with maximum average degree less than 8/3. The conjectures are already confirmed for larger families, but the structure theorems and reducibility results are of independent interest.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 4; 769-799
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A New Framework to Approach Vizing’s Conjecture
Autorzy:
Brešar, Boštjan
Hartnell, Bert L.
Henning, Michael A.
Kuenzel, Kirsti
Rall, Douglas F.
Powiązania:
https://bibliotekanauki.pl/articles/32222699.pdf
Data publikacji:
2021-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Cartesian product
total domination
Vizing’s conjecture
Clark and Suen bound
Opis:
We introduce a new setting for dealing with the problem of the domination number of the Cartesian product of graphs related to Vizing’s conjecture. The new framework unifies two different approaches to the conjecture. The most common approach restricts one of the factors of the product to some class of graphs and proves the inequality of the conjecture then holds when the other factor is any graph. The other approach utilizes the so-called Clark-Suen partition for proving a weaker inequality that holds for all pairs of graphs. We demonstrate the strength of our framework by improving the bound of Clark and Suen as follows: $ \gamma (X \square Y) \ge \max \{\frac{1}{2} \gamma (X) \gamma_t (Y), \frac{1}{2} \gamma_t (X) \gamma (Y) \} $, where $ \gamma $ stands for the domination number, $ \gamma_t $ is the total domination number, and $ X \square Y $ is the Cartesian product of graphs $X$ and $Y$.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 3; 749-762
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-8 z 8

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