Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2004/iii/paper-2/1/d/solution
Past exam of the mathematics course of the University of Cambridge 2004 iii Paper 2 1 d Solution by
Codex 0 Created 2026-10-03 Updated 2026-10-14
It suffices to centralize each minimal normal subgroup . The subgroup is normal in , so it is either or . In the first caseIn the second case is a nilpotent group. Its nontrivial group center is a characteristic subgroup of , hence normal in , so minimality makes abelian. The primary components, which are characteristic subgroups, and the subgroup killed by a prime show that is elementary abelian of exponent . Thus .
The finite p-group acts by conjugation on . Its orbits have prime-power sizes; hence the number of fixed elements is congruent to modulo . The identity is fixed, so there is a nonidentity fixed element. Therefore . This intersection is normal in , and minimality makes it . The other p-cores commute with , and hence with . Thus every factor of centralizes . Since the group socle is generated by these minimal normal subgroups,
New to topics? Read the docs here!