1. More results on the domination number of Cartesian product of two directed cyclesAnsheng Ye, Fang Miao, Zehui Shao, Jia-Bao Liu, Janez Žerovnik, Polona Repolusk, 2019, original scientific article Abstract: Let γ(D) denote the domination number of a digraph D and let C$_m$□C$_n$ denote the Cartesian product of C$_m$ and C$_n$, the directed cycles of length n ≥ m ≥ 3. Liu et al. obtained the exact values of γ(C$_m$□C$_n$) for m up to 6 [Domination number of Cartesian products of directed cycles, Inform. Process. Lett. 111 (2010) 36–39]. Shao et al. determined the exact values of γ(C$_m$□C$_n$) for m = 6, 7 [On the domination number of Cartesian product of two directed cycles, Journal of Applied Mathematics, Volume 2013, Article ID 619695]. Mollard obtained the exact values of γ(C$_m$□C$_n$) for m = 3k + 2 [M. Mollard, On domination of Cartesian product of directed cycles: Results for certain equivalence classes of lengths, Discuss. Math. Graph Theory 33(2) (2013) 387–394.]. In this paper, we extend the current known results on C$_m$□C$_n$ with m up to 21. Moreover, the exact values of γ(C$_n$□C$_n$) with n up to 31 are determined.
Keywords: domination number, Cartesian product, directed cycle
Published in DKUM: 02.09.2022; Views: 611; Downloads: 13
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2. L(2,1)-labeling of the strong product of paths and cyclesZehui Shao, Aleksander Vesel, 2014, original scientific article Abstract: An L(2,1)-labeling of a graph G = (V, E) is a function f from the vertex set V(G) to the set of nonnegative integers such that the labels on adjacent vertices differ by at least two and the labels on vertices at distance two differ by at least one. The span of f is the difference between the largest and the smallest numbers in f(V). The ƛ-number of G, denoted by ƛ(G), is the minimum span over all L(2,1)-labelings of G. We consider the ƛ-number of Pn ☒ Cm and for n ≤ 11 the ƛ-number of Cn ☒ Cm. We determine ƛ-numbers of graphs of interest with the exception of a finite number of graphs and we improve the bounds on the ƛ-number of Cn ☒ Cm, m ≥ 24 and n ≥ 26.
Keywords: mathematics, graph theory
Published in DKUM: 15.06.2017; Views: 1227; Downloads: 354
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3. A note on the chromatic number of the square of the Cartesian product of two cyclesZehui Shao, Aleksander Vesel, 2013, other scientific articles Abstract: The square ▫$G^2$▫ of a graph ▫$G$▫ is obtained from ▫$G$▫ by adding edges joining all pairs of nodes at distance 2 in ▫$G$▫. In this note we prove that ▫$chi((C_mBox C_n)^2) le 6$ for $m, n ge 40$▫. This confirms Conjecture 19 stated in [É. Sopena, J. Wu, Coloring the square of the Cartesian product of two cycles, Discrete Math. 310 (2010) 2327-2333].
Keywords: matematika, teorija grafov, kromatično število, kartezični produkt, označevanje grafov, kvadrat grafa, mathematics, graph theory, chromatic number, Cartesian product, graph labeling, square if a graph
Published in DKUM: 10.07.2015; Views: 1460; Downloads: 84
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