Abstract
A k-L(2,1)-labelling of a graph G is a mapping f:V(G)→{0,1,2,…,k} such that |f(u)−f(v)|≥2 if uv∈E(G) and f(u)≠f(v) if u,v are distance two apart. The smallest positive integer k such that G admits a k-L(2,1)-labelling is called the λ-number of G. In this paper we study this quantity for cubic Cayley graphs (other than the prism graphs) on dihedral groups, which are called brick product graphs or honeycomb toroidal graphs. We prove that the λ-number of such a graph is between 5 and 7, and moreover we give a characterisation of such graphs with λ-number 5.
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Acknowledgements
We appreciate the referees for their helpful comments. The work was supported by a Discovery Project Grant (DP0558677) of the Australia Research Council. Li was supported by a grant (11171129) of the National Natural Science Foundation of China. Zhou was supported by a Future Fellowship (FT110100629) and a Discovery Project Grant (DP120101081) of the Australian Research Council.
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Li, X., Mak-Hau, V. & Zhou, S. The L(2,1)-labelling problem for cubic Cayley graphs on dihedral groups. J Comb Optim 25, 716–736 (2013). https://doi.org/10.1007/s10878-012-9525-4
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DOI: https://doi.org/10.1007/s10878-012-9525-4