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L(2,1)-labeling of the strong product of paths and cycles
Zehui 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: 15.06.2017; Views: 589; Downloads: 266
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A note on the chromatic number of the square of the Cartesian product of two cycles
Zehui Shao, Aleksander Vesel, 2013, short scientific article

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: 10.07.2015; Views: 725; Downloads: 66
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