Domination Subdivision Numbers in Graphs

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A set S of vertices of a graph G = (V, E) is a dominating set if every vertex in V - S is adjacent to some vertex in 3. The domination number γ(G) is the minimum cardinality of a dominating set of G, and the domination subdivision number sdγ(G) is the minimum number of edges that must be subdivided (each edge in G can be subdivided at most once) in order to increase the domination number. In June 2000, Arumugam conjectured that 1 ≤ sdγ(G) ≤ 3 for any graph G. However, a counterexample to this conjecture given in [6] suggests the modified conjecture that 1 ≤ sdγ(G) ≤ 4 for any graph G. It is also conjectured in [6] that for every graph G with minimum degree δ(G) ≥ 2, sdγ(G) ≤ δ(G) + 1. In this paper we extend several previous results and consider evidence in support of these two conjectures.