Paired versus double domination in K1,r-free graphs

  • Authors:
  • Paul Dorbec;Bert Hartnell;Michael A. Henning

  • Affiliations:
  • LaBRI, Université de Bordeaux --- CNRS, Talence Cedex, France 33405;Department of Mathematics and Computing Science, Saint Mary's University, Halifax, Canada B3H 3C3;Department of Mathematics, University of Johannesburg, Auckland Park, South Africa 2006

  • Venue:
  • Journal of Combinatorial Optimization
  • Year:
  • 2014

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Abstract

A vertex in G is said to dominate itself and its neighbors. A subset S of vertices is a dominating set if S dominates every vertex of G. A paired-dominating set is a dominating set whose induced subgraph contains a perfect matching. The paired-domination number of a graph G, denoted by 驴 pr(G), is the minimum cardinality of a paired-dominating set in G. A subset S⊆V(G) is a double dominating set of G if S dominates every vertex of G at least twice. The minimum cardinality of a double dominating set of G is the double domination number 驴 脳2(G). A claw-free graph is a graph that does not contain K 1,3 as an induced subgraph. Chellali and Haynes (Util. Math. 67:161---171, 2005) showed that for every claw-free graph G, we have 驴 pr(G)≤驴 脳2(G). In this paper we extend this result by showing that for r驴2, if G is a connected graph that does not contain K 1,r as an induced subgraph, then $\gamma_{\mathrm{pr}}(G)\le ( \frac{2r^{2}-6r+6}{r(r-1)} )\gamma_{\times2}(G)$ .