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Wyświetlanie 1-5 z 5
Tytuł:
Almost-Rainbow Edge-Colorings of Some Small Subgraphs
Autorzy:
Krop, Elliot
Krop, Irina
Powiązania:
https://bibliotekanauki.pl/articles/30097998.pdf
Data publikacji:
2013-09-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Ramsey theory
generalized Ramsey theory
rainbow-coloring
edge-coloring
Erdös problem
Opis:
Let $ f(n, p, q) $ be the minimum number of colors necessary to color the edges of $ K_n $ so that every $ K_p $ is at least $ q $-colored. We improve current bounds on these nearly “anti-Ramsey” numbers, first studied by Erdös and Gyárfás. We show that $ f(n, 5, 0) \ge \frac{7}{4} n - 3 $, slightly improving the bound of Axenovich. We make small improvements on bounds of Erdös and Gyárfás by showing $ \frac{5}{6} n + 1 \leq f(n,4,5) $ and for all even $ n ≢ 1(\text{mod } 3) $, $ f(n, 4, 5) \leq n−1 $. For a complete bipartite graph $ G= K_{n,n}$, we show an $n$-color construction to color the edges of $ G $ so that every $ C_4 ⊆ G $ is colored by at least three colors. This improves the best known upper bound of Axenovich, Füredi, and Mubayi.
Źródło:
Discussiones Mathematicae Graph Theory; 2013, 33, 4; 771-784
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Erdős-Gallai-Type Results for Total Monochromatic Connection of Graphs
Autorzy:
Jiang, Hui
Li, Xueliang
Zhang, Yingying
Powiązania:
https://bibliotekanauki.pl/articles/31343240.pdf
Data publikacji:
2019-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
total-colored graph
total monochromatic connection
Erdős- Gallai-type problem
Opis:
A graph is said to be total-colored if all the edges and the vertices of the graph are colored. A total-coloring of a graph is a total monochromatically-connecting coloring (TMC-coloring, for short) if any two vertices of the graph are connected by a path whose edges and internal vertices have the same color. For a connected graph G, the total monochromatic connection number, denoted by tmc(G), is defined as the maximum number of colors used in a TMC-coloring of G. In this paper, we study two kinds of Erdős-Gallai-type problems for tmc(G) and completely solve them.
Źródło:
Discussiones Mathematicae Graph Theory; 2019, 39, 4; 775-785
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rainbow Total-Coloring of Complementary Graphs and Erdős-Gallai Type Problem For The Rainbow Total-Connection Number
Autorzy:
Sun, Yuefang
Jin, Zemin
Tu, Jianhua
Powiązania:
https://bibliotekanauki.pl/articles/31342242.pdf
Data publikacji:
2018-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Rainbow total-coloring
rainbow total-connection number
complementary graph
Erdős-Gallai type problem
Opis:
A total-colored graph $G$ is rainbow total-connected if any two vertices of $G$ are connected by a path whose edges and internal vertices have distinct colors. The rainbow total-connection number, denoted by $ rtc(G) $, of a graph $G$ is the minimum number of colors needed to make $G$ rainbow total-connected. In this paper, we prove that $ rtc(G) $ can be bounded by a constant 7 if the following three cases are excluded: $ diam( \overline{G} ) = 2 $, $ diam( \overline{G} ) = 3 $, $ \overline{G} $ contains exactly two connected components and one of them is a trivial graph. An example is given to show that this bound is best possible. We also study Erdős-Gallai type problem for the rainbow total-connection number, and compute the lower bounds and precise values for the function $ f(n, k) $, where $ f(n, k) $ is the minimum value satisfying the following property: if $ |E(G)| \ge f(n, k) $, then $ rtc(G) \le k $.
Źródło:
Discussiones Mathematicae Graph Theory; 2018, 38, 4; 1023-1036
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
More on the Rainbow Disconnection in Graphs
Autorzy:
Bai, Xuqing
Chang, Renying
Huang, Zhong
Li, Xueliang
Powiązania:
https://bibliotekanauki.pl/articles/32222544.pdf
Data publikacji:
2022-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge-coloring
edge-connectivity
rainbow disconnection coloring (number)
Erdős-Gallai type problem
Nordhaus-Gaddum type bounds
complexity
NP-hard (complete)
Opis:
Let G be a nontrivial edge-colored connected graph. An edge-cut R of G is called a rainbow-cut if no two of its edges are colored the same. An edge-colored graph G is rainbow disconnected if for every two vertices u and v of G, there exists a u-v-rainbow-cut separating them. For a connected graph G, the rainbow disconnection number of G, denoted by rd(G), is defined as the smallest number of colors that are needed in order to make G rainbow disconnected. In this paper, we first determine the maximum size of a connected graph G of order n with rd(G) = k for any given integers k and n with 1 ≤ k ≤ n − 1, which solves a conjecture posed only for n odd in [G. Chartrand, S. Devereaux, T.W. Haynes, S.T. Hedetniemi and P. Zhang, Rainbow disconnection in graphs, Discuss. Math. Graph Theory 38 (2018) 1007–1021]. From this result and a result in their paper, we obtain Erdős-Gallai type results for rd(G). Secondly, we discuss bounds on rd(G) for complete multipartite graphs, critical graphs with respect to the chromatic number, minimal graphs with respect to the chromatic index, and regular graphs, and we also give the values of rd(G) for several special graphs. Thirdly, we get Nordhaus-Gaddum type bounds for rd(G), and examples are given to show that the upper and lower bounds are sharp. Finally, we show that for a connected graph G, to compute rd(G) is NP-hard. In particular, we show that it is already NP-complete to decide if rd(G) = 3 for a connected cubic graph. Moreover, we show that for a given edge-colored (with an unbounded number of colors) connected graph G it is NP-complete to decide whether G is rainbow disconnected.
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 4; 1185-1204
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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