Module

RingFiniteTameCharacter.lean

Nyll.ValuedFieldTheory.Ramification.HilbertRamification.RingFiniteTameCharacter
6 declarations indexed from sourceView source ↗

Finite tame characters of discrete valuation rings

Defines the tame order as the size of the inertia-character image and constructs a surjective character onto all roots of unity of that order. It identifies the principal-unit kernel and produces a primitive root in the residue field.

Declarations

RamificationTheory.HilbertRamification.DiscreteValuationRing.tameOrder

The order of the image of the actual, constructed DVR inertia character.

Source context 6 commands

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

noncomputable section
namespace RamificationTheory.HilbertRamification.DiscreteValuationRing
open IsLocalRing
universe u v
variable (R : Type u) [CommRing R] [IsDomain R] [IsDiscreteValuationRing R]
variable (G : Type v) [Group G] [MulSemiringAction G R]
def tameOrder : ℕ
RamificationTheory.HilbertRamification.DiscreteValuationRing.tameOrder_pos
Source context 7 commands

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

noncomputable section
namespace RamificationTheory.HilbertRamification.DiscreteValuationRing
open IsLocalRing
universe u v
variable (R : Type u) [CommRing R] [IsDomain R] [IsDiscreteValuationRing R]
variable (G : Type v) [Group G] [MulSemiringAction G R]
variable [Finite G]
theorem tameOrder_pos : 0 < tameOrder R G
RamificationTheory.HilbertRamification.DiscreteValuationRing.tameCharacter

The actual finite DVR inertia character with its full root-group target.

Source context 7 commands

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

noncomputable section
namespace RamificationTheory.HilbertRamification.DiscreteValuationRing
open IsLocalRing
universe u v
variable (R : Type u) [CommRing R] [IsDomain R] [IsDiscreteValuationRing R]
variable (G : Type v) [Group G] [MulSemiringAction G R]
variable [Finite G]
def tameCharacter : (maximalIdeal R).inertia G →*
    rootsOfUnity (tameOrder R G) (ResidueField R)
RamificationTheory.HilbertRamification.DiscreteValuationRing.tameCharacter_surjective
Source context 7 commands

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

noncomputable section
namespace RamificationTheory.HilbertRamification.DiscreteValuationRing
open IsLocalRing
universe u v
variable (R : Type u) [CommRing R] [IsDomain R] [IsDiscreteValuationRing R]
variable (G : Type v) [Group G] [MulSemiringAction G R]
variable [Finite G]
theorem tameCharacter_surjective : Function.Surjective (tameCharacter R G)
RamificationTheory.HilbertRamification.DiscreteValuationRing.tameCharacter_ker

The full root-codomain character has the actual principal-unit kernel.

Source context 7 commands

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

noncomputable section
namespace RamificationTheory.HilbertRamification.DiscreteValuationRing
open IsLocalRing
universe u v
variable (R : Type u) [CommRing R] [IsDomain R] [IsDiscreteValuationRing R]
variable (G : Type v) [Group G] [MulSemiringAction G R]
variable [Finite G]
theorem tameCharacter_ker :
    (tameCharacter R G).ker = principalUnitInertia R G
RamificationTheory.HilbertRamification.DiscreteValuationRing.exists_primitiveRoot_tameOrder

All finite tame orders occur as actual primitive roots in the residue field.

Source context 7 commands

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

noncomputable section
namespace RamificationTheory.HilbertRamification.DiscreteValuationRing
open IsLocalRing
universe u v
variable (R : Type u) [CommRing R] [IsDomain R] [IsDiscreteValuationRing R]
variable (G : Type v) [Group G] [MulSemiringAction G R]
variable [Finite G]
theorem exists_primitiveRoot_tameOrder :
    ∃ ζ : ResidueField R, IsPrimitiveRoot ζ (tameOrder R G)