Module

PrimePowerRoots.lean

Nyll.ValuedFieldTheory.LocalField.DiscreteValuationField.PrincipalUnits.PrimePowerRoots
1 declaration indexed from sourceView source ↗

Field roots of principal units remain in the principal-unit group

A field element whose p-power is a principal unit is represented by an actual element of the principal-unit subgroup, with the same power there. This is the root used when taking logarithms of a Kummer relation.

Declarations

LocalFieldTheory.DiscreteValuationField.CompleteDVF.higherPrincipalUnitGroup.exists_primePower_root_of_field_root

A prime-power root in the field lifts to a root in the actual first principal-unit group; its underlying field element is the prescribed root.

Source context 3 commands

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

namespace LocalFieldTheory.DiscreteValuationField.CompleteDVF.higherPrincipalUnitGroup
universe u v
variable {K : Type u} [Field K]
theorem exists_primePower_root_of_field_root
    (F : ValuationTheory.DiscreteValuationField.CompleteDVF.{u, v} K)
    (p : ℕ) [Fact p.Prime] [hres : CharP F.residueField p]
    (s : ℕ) (y : K) (u : higherPrincipalUnitGroup F 1)
    (hy : y ^ (p ^ s) = (((u : F.valuationSubringˣ) : F.valuationSubring) : K)) :
    ∃ z : higherPrincipalUnitGroup F 1,
      (((z : F.valuationSubringˣ) : F.valuationSubring) : K) = y ∧
      z ^ (p ^ s) = u