如何判断两个系统不同构？ Example 9.5.Even though S3 and Z6 possess the same number of elements,we would suspect that they are not isomorphic,because Z6 is abelian and S3 is nonabelian.To demonstrate that this is indeed the case,suppose that Z6-S3 is an isomorphism.Let a,b e S3 be two elements such that ab ba.Since o is an isomorphism,there exist elements m and n in Z6 such that o(m)=a and o(n)=b. However, ab =o(m)o(n)=o(m+n)=o(n+m)=o(n)o(m)=ba, which contradicts the fact that a and b do not commute如何判断两个系统不同构？