The Domatic Number of Regular Graphs

The domatic number of a graph G is the maximum number of dominating sets into which the vertex set of G can be partitioned. We show that the domatic number of a random r-regular graph is almost surely at most r, and that for 3-regular random graphs, the domatic number is almost surely equal to 3. We also give a lower bound on the domatic number of a graph in terms of order, minimum degree and maximum degree. As a corollary, we obtain the result that the domatic number of an r-regular graph is at least (r + 1)/(3ln(r + 1)).