Module

AbelianUnitMonodromyKernel.lean

Nyll.EtaleFundamentalGroups.GeometricFiber.AbelianUnitMonodromyKernel
2 declarations indexed from sourceView source ↗

The kernel of actual multiplication monodromy

The stabilizer of the actual unit point is the image of the fundamental group of the multiplication cover. The actual pointed map of multiplication induces the corresponding power map on the fundamental group.

Declarations

GoodReductionJacobian.RelativeGroupLaw.UnitMultiplication.unit_eq_liftedPoint

The distinguished torsion-fibre unit is the actual lift of the unit section.

Source context 4 commands

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

noncomputable section
open CategoryTheory AlgebraicGeometry AlgebraicGeometry.FiniteEtale
namespace GoodReductionJacobian.RelativeGroupLaw.UnitMultiplication
variable {K : Type} [Field K] [IsSepClosed K]
  {A : Scheme} {f : A ⟶ Spec (.of K)} [IsProper f] [Smooth f]
  (G : RelativeGroupLaw K f) (hc : G.IsCommutative)
theorem unit_eq_liftedPoint (n : unitIndices K) :
    unit G hc n =
      (fiberObjEquivHom (G.one (𝟙 (Spec (.of K)))).1 (cover G hc n)).symm
        (Over.homMk (G.one (𝟙 (Spec (.of K)))).1 (G.unit_comp_schemeNsmul (n.1 : ℕ)))
GoodReductionJacobian.RelativeGroupLaw.UnitMultiplication.monodromy_eq_zero_iff_exists_pow

Vanishing at the actual torsion level means being an actual n-th power in the original fundamental group.

Source context 4 commands

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

noncomputable section
open CategoryTheory AlgebraicGeometry AlgebraicGeometry.FiniteEtale
namespace GoodReductionJacobian.RelativeGroupLaw.UnitMultiplication
variable {K : Type} [Field K] [IsSepClosed K]
  {A : Scheme} {f : A ⟶ Spec (.of K)} [IsProper f] [Smooth f]
  (G : RelativeGroupLaw K f) (hc : G.IsCommutative)
theorem monodromy_eq_zero_iff_exists_pow [GeometricallyConnected f]
    (n : unitIndices K) (g : π₁ᵉᵗ((G.one (𝟙 (Spec (.of K)))).1)) :
    monodromy G hc n g = 0 ↔
      ∃ a : π₁ᵉᵗ((G.one (𝟙 (Spec (.of K)))).1), a ^ (n.1 : ℕ) = g