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Theorems · Theorem · group theory

alternatingGroup.isConj_swap_mul_swap_of_cycleType_two

Deprecated since 2026-04-28Mathlib marks this declaration as deprecated.

∀ {g : Equiv.Perm (Fin 5)},
  g ∈ alternatingGroup (Fin 5) → g ≠ 1 → (∀ n ∈ g.cycleType, n = 2) → IsConj (Equiv.swap 0 4 * Equiv.swap 1 3) g

Shows that any non-identity element of $A_5$ whose cycle decomposition consists only of swaps is conjugate to $(04)(13)$. This is used to show that the normal closure of such a permutation in $A_5$ is $A_5$.

Defined in
Mathlib.GroupTheory.SpecificGroups.Alternating
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Foundations
Depth 103 from the axioms · uses propext, Classical.choice, Quot.sound

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