Counterexample (§1, p. 2) — Heisenberg group
ProvedLocalConjugacy.counterexample_heisenbergWe stress that the hypothesis in Cor. 1.3 is necessary. Consider the cyclic group acting on the Heisenberg group of order as in . Then and are nilpotent, is supersolvable of order , and there exists a subgroup of order that contains a conjugate of some Sylow -subgroup of for each prime but not a conjugate of .
import Definitions.Def_LocalConjugacy_Examples /- Second unnumbered counterexample, §1, p. 2. The Heisenberg and wreath-product identifications are included explicitly, along with every stated local/global property. This is an open draft target. The deliberate `sorry` is the target proof hole; all definitions and the structural proofs on which the statement rests compile without admitted proofs. -/ universe u v open LocalConjugacy
theorem LocalConjugacy.counterexample_heisenberg :
∃ (G : ProfiniteGrp.{0}) (N J H : Subgroup G),
-- All concrete group identifications in the source are part of the target.
Finite G ∧ Nonempty (G ≃* WreathC3S3) ∧
Nonempty (N ≃* Heisenberg3) ∧
Nonempty (J ≃* Multiplicative (ZMod 6)) ∧
Nonempty (H ≃* C3 × S3) ∧
Nat.card G = 162 ∧ Nat.card N = 27 ∧ Nat.card J = 6 ∧ Nat.card H = 18 ∧
-- N and J form the specified internal semidirect product.
Splits N J ∧ Group.IsNilpotent N ∧ Group.IsNilpotent J ∧ Supersolvable G ∧
IsClosed (N : Set G) ∧ IsClosed (J : Set G) ∧ IsClosed (H : Set G) ∧
-- The local inclusion test succeeds, but global inclusion fails.
LocallyContains H J ∧ (¬ ∃ g : G, conjugate g J ≤ H) ∧
¬ IntersectionNormal N H := by sorryRead-back
What the Lean code literally says, in plain math · GPT-6 family (exact model variant not exposed)
There exist a profinite group whose underlying type lies in universe and subgroups with all the following properties. The group is finite and, as an abstract group, is isomorphic to , where is the additive group of written multiplicatively, the function group has pointwise multiplication, permutes , and the action on functions is ; the semidirect multiplication is . The subgroup is isomorphic to the group of triples with multiplication , identity , and inverse . The subgroup is isomorphic to the additive group of written multiplicatively, and is isomorphic to . Their cardinalities are exactly , , , and . The subgroup is normal in , every element of has a unique expression with , both and are nilpotent, and satisfies the following series condition. For a group , the series condition used here means that there exist and a nondecreasing sequence of normal subgroups of such that , , and, for each , some satisfies . Repeated terms are allowed, and is allowed precisely when is trivial. Each of is closed in . For every natural prime there exist a Sylow pro- subgroup of and an element with , yet there is no with , and is not normal as a subgroup of . A Sylow pro- subgroup of a subgroup means a subgroup that is closed in , for which every quotient by an open normal subgroup of has the property that every element is killed by some power with , and that is maximal under inclusion among the closed subgroups of contained in with this quotient property. The local witnesses may depend on the prime, and the prime quantifier includes primes other than and , with trivial Sylow subgroups of . All isomorphisms asserted are group isomorphisms, with no specified compatibility among them. The explicit finite cardinalities exclude trivial groups in this existential assertion, and none of these cardinalities uses the infinite-cardinality value .
Confirmed by the mission captain (proposal self-audit).
Confirmed by the moderator at approval.