Module

AbelianMultiplicationCharacters.lean

Nyll.EtaleFundamentalGroups.GeometricFiber.AbelianMultiplicationCharacters
1 declaration indexed from sourceView source ↗

Finite-exponent characters factor through actual multiplication covers

The full Tate comparison and the explicit kernel calculation show that a character killed by n factors through monodromy of the actual n-multiplication cover. This uses the same integer n, without a larger auxiliary level.

Declarations

GoodReductionJacobian.RelativeGroupLaw.character_factors_multiplicationMonodromy

A character of exponent dividing n is evaluated on the actual n-torsion displacement of the multiplication cover.

Source context 3 commands

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

noncomputable section
open CategoryTheory AlgebraicGeometry
namespace GoodReductionJacobian.RelativeGroupLaw
theorem character_factors_multiplicationMonodromy
    {K : Type} [Field K] [IsAlgClosed K] [CharZero K]
    {J : Scheme} {b : J ⟶ Spec (.of K)}
    [IsProper b] [Smooth b] [GeometricallyConnected b]
    (G : RelativeGroupLaw K b) (hc : G.IsCommutative)
    {H : Type} [AddCommGroup H] (n : ℕ+)
    (χ : π₁ᵉᵗ((G.one (𝟙 (Spec (.of K)))).1) →* Multiplicative H)
    (hH : ∀ a : H, (n : ℕ) • a = 0) :
    ∃ ψ : ProCGroups.torsionLevel (G.AlgPoints hc K) n →+ H,
      ∀ g, ψ (G.multiplicationMonodromy hc n g) = (χ g).toAdd