Domination in Graphs of Minimum Degree at least Two and Large Girth

Abstract

We prove that for graphs of order n, minimum degree δ ≥ 2 and girth g ≥ 5 the domination number γ satisfies \(\gamma\leq\left(\frac{1}{3}+\frac{2}{3g}\right)n\). As a corollary this implies that for cubic graphs of order n and girth g ≥ 5 the domination number γ satisfies \(\gamma \leq \left(\frac{44}{135}+\frac{82}{135g}\right)n\) which improves recent results due to Kostochka and Stodolsky (An upper bound on the domination number of n-vertex connected cubic graphs, manuscript (2005)) and Kawarabayashi, Plummer and Saito (Domination in a graph with a 2-factor, J. Graph Theory 52 (2006), 1–6) for large enough girth. Furthermore, it confirms a conjecture due to Reed about connected cubic graphs (Paths, stars and the number three, Combin. Prob. Comput. 5 (1996), 267–276) for girth at least 83.