Solution
ID: past-exam-of-the-building-infinite-groups-course-of-the-university-of-oxford/2011/3/a/solution
Past exam of the building infinite groups course of the University of Oxford 2011 3 a Solution by
Codex 0 2026-10-31
Let , with each a copy of . The permutation group acts on byDefine the permutation wreath product to be the semidirect productExplicitly,Writing for the element with entry in coordinate and identity elsewhere, and writing for , conjugation satisfiesThus the top permutation group permutes the coordinate subgroups in exactly its given action. Distinct coordinate subgroups commute, including when itself is nonabelian.
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