科研之友
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摘要
For any refinement of a star graph G with a center c, let G(c)* be the subgraph of G induced on the vertex set V(G)\{c or end vertices adjacent to c}. In this article, it is proved that almost all commutative zero-divisor semigroups S satisfy S-3 = 0, S-2 = {0, c} if Gamma(S) is a refinement of a star graph with a center c such that Gamma(S)(c)* is one of the following finite or infinite graphs: the Pascal triangle graphs, the plane lattice graphs, the web graphs. When the graph Gamma(S) is finite, we also obtain formulas to count the number of mutually non-isomorphic corresponding semigroups.
- 出版日期2010
- 单位上海交通大学
