On independent domination number of regular graphs

Let G be a simple graph. The independent domination number i(G) is the minimum cardinality among all maximal independent sets of G. Haviland (1995) conjectured that any connected regular graph G of order n and degree δ ≤ n/2 satisfies i(G) ≤ [2n/3δ]δ/2. In this paper, we will settle the conjecture of Haviland in the negative by constructing counterexamples. Therefore a larger upper bound is expected. We will also show that a connected cubic graph G of order n ≥ 8 satisfies i(G) ≤ 2n/5, providing a new upper bound for cubic graphs.