Module

LocalTameRootsPowerMap.lean

Nyll.ValuedFieldTheory.Ramification.HilbertRamification.LocalTameRootsPowerMap
3 declarations indexed from sourceView source ↗

Power maps on local tame root groups

Defines power homomorphisms on the local tame root group and proves injectivity for exponential- characteristic powers. These maps are surjective when the acting group is finite.

Declarations

RamificationTheory.HilbertRamification.DiscreteValuationRing.localTameRootsPowerGroupMap

The canonical power map on the actual finite root group.

Source context 5 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]
  (G : Type v) [Group G] [MulSemiringAction G R]
def localTameRootsPowerGroupMap (m : ℕ) :
    localTameRootsGroupObject R G →* localTameRootsGroupObject R G
RamificationTheory.HilbertRamification.DiscreteValuationRing.localTameRootsPowerGroupMap_injective

Exponential-characteristic powers are injective on the actual roots, by the native residue-field Frobenius argument.

Source context 5 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]
  (G : Type v) [Group G] [MulSemiringAction G R]
theorem localTameRootsPowerGroupMap_injective
    (p a : ℕ) [ExpChar (ResidueField R) p] :
    Function.Injective (localTameRootsPowerGroupMap R G (p ^ a))
RamificationTheory.HilbertRamification.DiscreteValuationRing.localTameRootsPowerGroupMap_surjective

Exponential-characteristic power maps are bijective on these actual finite root groups, with no perfectness premise.

Source context 5 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]
  (G : Type v) [Group G] [MulSemiringAction G R]
theorem localTameRootsPowerGroupMap_surjective [Finite G]
    (p a : ℕ) [ExpChar (ResidueField R) p] :
    Function.Surjective (localTameRootsPowerGroupMap R G (p ^ a))