讨论了竞赛图的零因子半群.一个半群S的零因子图是一个有向图Г(S),其顶点是S中非零的零因子,S中两个不同的元x,y有一条有向边x→y当且仅当xy=0.该文证明了如果S是一个没有非零幂零元的有限半群且图Г(S)的顶点数大于1,那么图Г(S)不是一个竞赛图.另外对于任意的正整数n,该文完全决定了顶点数为n蹬任一个竞赛图的所有零因子半群.
In this paper, we study the zero- divisor semigroups of tournaments. Define the zero- divisor graph of a semigroup S as the directed graph Г( S ) whose vertices are nonzero zero - divisors of S with edges x→y if xy = 0 and x≠y. It has been shown that the graph Г(s) is not a tournament if S is a finite reduced sernigroup and Г(s) has more than one vertex. We have determined all the zero - divisor semigroups of each tournament with n vertices, for any positive integer n.