Dominating a Family of Graphs with Small Connected Subgraphs

  • Authors:
  • Yair Caro;Raphael Yuster

  • Affiliations:
  • Department of Mathematics, University of Haifa-Oranim, Tivon 36006, Israel (e-mail: yairc@macam98.ac.il, raphy@macam98.ac.il);Department of Mathematics, University of Haifa-Oranim, Tivon 36006, Israel (e-mail: yairc@macam98.ac.il, raphy@macam98.ac.il)

  • Venue:
  • Combinatorics, Probability and Computing
  • Year:
  • 2000

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Abstract

Let F = {G1, …, Gt} be a family of n-vertex graphs defined on the same vertex-set V, and let k be a positive integer. A subset of vertices D ⊂ V is called an (F, k)-core if, for each v ∈ V and for each i = 1, …, t, there are at least k neighbours of v in Gi that belong to D. The subset D is called a connected (F, k)-core if the subgraph induced by D in each Gi is connected. Let δi be the minimum degree of Gi and let δ(F) = minti=1δi. Clearly, an (F, k)-core exists if and only if δ(F) ≥ k, and a connected (F, k)-core exists if and only if δ(F) ≥ k and each Gi is connected. Let c(k, F) and cc(k, F) be the minimum size of an (F, k)-core and a connected (F, k)-core, respectively. The following asymptotic results are proved for every t k F. The results unify and extend related results on dominating sets, strong dominating sets and connected dominating sets.