Some matching properties in 4-γ×2--critical graphs

  • Authors:
  • Haichao Wang;Erfang Shan

  • Affiliations:
  • Department of Mathematics, Shanghai University, Shanghai 200444, China and Department of Mathematics and Physics, Shanghai University of Electric Power, Shanghai 200090, China;Department of Mathematics, Shanghai University, Shanghai 200444, China

  • Venue:
  • Computers & Mathematics with Applications
  • Year:
  • 2010

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Abstract

A vertex subset S of a graph G=(V,E) is a double dominating set for G if |N[v]@?S|=2 for each vertex v@?V, where N[v]={u|uv@?E}@?{v}. The double domination number of G, denoted by @c"x"2(G), is the cardinality of a smallest double dominating set of G. A graph G is said to be double domination edge critical if @c"x"2(G+e)=6 except a family of graphs. Secondly, we show that G is bicritical if G is a 2-connected claw-free 4-@c"x"2(G)-critical graph of even order with minimum degree at least 3. Finally, we show that G is bicritical if G is a 3-connected K"1","4-free 4-@c"x"2(G)-critical graph of even order with minimum degree at least 4.