Module

H2InflationRangeCardinality.lean

Nyll.GaloisCohomology.ProP.H2InflationRangeCardinality
2 declarations indexed from sourceView source ↗

Cardinality bounds on finite-stage degree-two inflation

A uniform bound p^d on finite-stage inflation images gives finite continuous H² of dimension at most d. Finiteness of the finite-stage cohomology and its image is constructed, rather than assumed.

Imports5
Imported by2

Declarations

ClassFieldTower.Cohomology.h2InflationRangeCanonicalZModAddCommGroup
Source context 6 commands

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

open scoped Topology
namespace ClassFieldTower.Cohomology
open ProCGroups ProCGroups.ProC
noncomputable section
universe u
variable {p : ℕ} [Fact p.Prime]
instance h2InflationRangeCanonicalZModAddCommGroup : AddCommGroup (ZMod p)
ClassFieldTower.Cohomology.finiteDimensional_and_finrank_degree_two_le_of_inflationRange_natCard

A uniform cardinality bound for finite-stage images bounds the full continuous degree-two cohomology dimension.

Source context 9 commands

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

open scoped Topology
namespace ClassFieldTower.Cohomology
open ProCGroups ProCGroups.ProC
noncomputable section
universe u
variable {p : ℕ} [Fact p.Prime]
local instance h2InflationRangeCanonicalZModAddCommGroup : AddCommGroup (ZMod p) :=
  (ZMod.instField p).toDivisionRing.toAddCommGroup
variable {G : Type u} [Group G] [TopologicalSpace G] [IsTopologicalGroup G]
variable [CompactSpace G] [T2Space G] [TotallyDisconnectedSpace G]
theorem finiteDimensional_and_finrank_degree_two_le_of_inflationRange_natCard
    (d : ℕ)
    (hG : HasOpenNormalBasisInClass (FiniteGroupClass.pGroup p) G)
    (hcard : ∀ U : OpenNormalSubgroupInClass (FiniteGroupClass.pGroup p) G,
      Nat.card (degreeTwoInflationRange (p := p) U) ≤ p ^ d) :
    FiniteDimensional (ZMod p) (continuousCohomologyZModPLifted p G 2) ∧
      Module.finrank (ZMod p) (continuousCohomologyZModPLifted p G 2) ≤ d