Module

TorsionCardinality.lean

Nyll.JacobianVarieties.Picard.TorsionCardinality
1 declaration indexed from sourceView source ↗

Cardinality of actual multiplication torsion

The cardinality is computed from the finite étale multiplication kernel and the geometric degree of multiplication. No cardinality or rank hypothesis is imposed on the group of algebraic points.

Declarations

GoodReductionJacobian.RelativeGroupLaw.natCard_torsionLevel_eq_pow

A positive multiplication kernel of a proper smooth commutative group scheme of dimension d has exactly n ^ (2 * d) algebraic points in characteristic zero.

Source context 5 commands

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

noncomputable section
open CategoryTheory AlgebraicGeometry NeronModelInfra
open AlgebraicCurves.Geometry.AbelianSchemes.Theorems.Proofs
open RelativeGroupLaw_isFinite_endKerStr_and_natCard_eq_endDegree_of_etale.P2mSepKer
namespace GoodReductionJacobian.RelativeGroupLaw
theorem natCard_torsionLevel_eq_pow
    {K : Type} [Field K] [IsAlgClosed K] [CharZero K]
    {A : Scheme.{0}} {f : A ⟶ Spec (CommRingCat.of K)}
    (G : RelativeGroupLaw K f) (hc : G.IsCommutative)
    (hA : AbelianSchemePropertyBundle K f)
    (d : ℕ) [SmoothOfRelativeDimension d f] (n : ℕ+) :
    Nat.card (ProCGroups.torsionLevel (G.AlgPoints hc K) n) =
      (n : ℕ) ^ (2 * d)