Graphs with Large Double Domination Numbers
نویسنده
چکیده
In a graph G, a vertex dominates itself and its neighbors. 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 γ×2(G). If G 6= C5 is a connected graph of order n with minimum degree at least 2, then we show that γ×2(G) ≤ 3n/4 and we characterize those graphs achieving equality.
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