Let G be a group,and let →/ΓC(G) be a digraph whose vertices are the nontrivial conjugacy classes of G and there is an arc from a vertex C to a vertex C' if and only if C≠C' and(C)■(C').In this paper,we characteri...
In this short note we prove that the finite non-abelian simple groups PSL(2,q),where g=5,7,are determincd by their posets of classes of isomorphic subgroups.Several interesting open problems are also formulated.