On average lower independence and domination numbers in graphs

Theaverage lower independencenumber iav(G)of a graphG=(V ,E) is defined as 1 |V | ∑ v∈V iv(G), and the average lower domination number av(G) is defined as 1 |V | ∑ v∈V v(G), where iv(G) (resp. v(G)) is the minimum cardinality of a maximal independent set (resp. dominating set) that contains v.We give an upper bound of iav(G) and av(G) for arbitrary graphs. Then we characterize the graphs achieving this upper bound for iav and for av respectively. © 2005 Elsevier B.V. All rights reserved.