Lower and upper orientable strong radius and strong diameter of complete k-partite graphs

  • Authors:
  • Huifang Miao;Xiaofeng Guo

  • Affiliations:
  • School of Mathematical Sciences, Xiamen University, Xiamen Fujian, PR China;School of Mathematical Sciences, Xiamen University, Xiamen Fujian, PR China

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2006

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Abstract

For two vertices u and v in a strong digraph D, the strong distance sd(u, v) between u and v is the minimum size (the number of arcs) of a strong sub-digraph of D containing u and v. For a vertex v of D, the strong eccentricity se(v) is the strong distance between v and a vertex farthest from v. The strong radius srad(D) (resp. strong diameter sdiam(D)) is the minimum (resp. maximum) strong eccentricity among the vertices of D. The lower (resp. upper) orientable strong radius srad(G) (resp. SRAD(G)) of a graph G is the minimum (resp. maximum) strong radius over all strong orientations of G. The lower (resp. upper) orientable strong diameter sdiam(G) (resp. SDIAM(G)) of a graph G is the minimum (resp. maximum) strong diameter over all strong orientations of G. In this paper, we determine the lower orientable strong radius and diameter of complete k-partite graphs, and give the upper orientable strong diameter and the bounds on the upper orientable strong radius of complete k-partite graphs. We also find an error about the lower orientable strong diameter of complete bipartite graph Km.n given in [Y.-L. Lai, F.-H. Chiang, C.-H. Lin, T.-C. Yu, Strong distance of complete bipartite graphs, The 19th Workshop on Combinatorial Mathematics and Computation Theory, 2002, pp. 12-16], and give a rigorous proof of a revised conclusion about sdiam(Km.n).