Module

CountableRelatorTarget.lean

Nyll.ProCGroups.GolodShafarevich.CountableRelatorTarget
1 declaration indexed from sourceView source ↗

The countable GS quotient of the presented group

The quotient of the free source factors continuously through the original presentation. Killing the images of the added relators therefore still surjects onto the infinite source quotient.

Declarations

ClassFieldTower.ProP.FiniteProPPresentation.infinite_target_quotient_of_countable_relator_budget

The actual presented group remains infinite after killing the images of a countable deep relator family within the displayed GS budget.

Source context 8 commands

Surrounding namespaces, section variables, and local commands at this declaration.

namespace ClassFieldTower.ProP.FiniteProPPresentation
open ProCGroups ProCGroups.Presentations
noncomputable section
universe u
variable {p d r : ℕ} [Fact p.Prime]
variable {sourceData :
  FreeProC.EpimorphicallyFreeProCGroupOnConvergingSetData.{u, u}
    (FiniteGroupClass.pGroup p)}
variable {G : Type u} [Group G] [TopologicalSpace G] [IsTopologicalGroup G]
variable [CompactSpace G] [T2Space G] [TotallyDisconnectedSpace G]
theorem infinite_target_quotient_of_countable_relator_budget
    (P : FiniteProPPresentation p d r sourceData G)
    (ν₀ : Fin r → ℕ)
    (hν₀ : ∀ i, P.RelatorZassenhausDepthAtLeast (ν₀ i) i)
    (f : ℕ → sourceData.carrier) (ν : ℕ → ℕ)
    (hν : ∀ n, ZassenhausDepthAtLeast p (ν n) (f n))
    {t : ℝ} (ht0 : 0 ≤ t) (ht1 : t < 1)
    (hbudget : ∀ N, 1 - (d : ℝ) * t +
      (∑ i : Fin r, t ^ ν₀ i) + (∑ i : Fin N, t ^ ν i) ≤ 0) :
    Infinite (G ⧸ closedNormalClosure (Set.range (P.quotient ∘ f)))