On a Vizing-like conjecture for direct product graphs

Abstract Let γ ( G ) be the domination number of a graph G , and let G × H be the direct product of graphs G and H . It is shown that for any k ⩾ 0 there exists a graph G such that γ ( G × G ) ⩽ γ ( G ) 2 − k . This in particular disproves a conjecture from [5].