The Frobenius iterates of `Oδ = O[X]/(Φ)` extend to automorphisms `τ i` of `Kδ = Frac Oδ` fixing `K`;
ProvedTypeDensity.frobenius_fraction_extensiontype-density
The Frobenius iterates of Oδ = O[X]/(Φ) extend to automorphisms τ i of Kδ = Frac Oδ fixing K; τ is a group action of ℕ with τ δ = id, and the fixed field of τ 1 is K.
Preamble
import Definitions.Def_TypeDensity_Basic import Definitions.Def_TypeDensity_Formula_LawAlgebra import Definitions.Def_TypeDensity_Algebra_AlgebraType import Definitions.Def_TypeDensity_Measure_AdicCylinders import Definitions.Def_TypeDensity_Measure_HenselProducts import Definitions.Def_TypeDensity_Unramified_Extension import Definitions.Def_TypeDensity_Measure_PrimitiveLocus import Definitions.Def_TypeDensity_Algebra_FactorInvariant import Theorems.Thm_TypeDensity_frobenius_fixed_ring import Theorems.Thm_TypeDensity_frobenius_pow_degree_eq_id import Theorems.Thm_TypeDensity_unramified_is_dvr import Mathlib.FieldTheory.RatFunc.Basic import Mathlib.MeasureTheory.Measure.Haar.Unique import Mathlib.NumberTheory.ArithmeticFunction.Moebius import Mathlib.NumberTheory.Padics.PadicIntegers import Mathlib.RingTheory.IntegralClosure.IntegralRestrict import Mathlib.RingTheory.MvPowerSeries.Basic import Mathlib.RingTheory.RamificationInertia.Basic import Mathlib.Topology.Algebra.Nonarchimedean.AdicTopology import Mathlib.FieldTheory.Finite.GaloisField import Mathlib.RingTheory.AdicCompletion.Algebra import Mathlib.RingTheory.RegularLocalRing.Defs import Mathlib.RingTheory.Henselian import Mathlib.Topology.Algebra.MvPolynomial import Mathlib.Algebra.Group.Pi.Units import Mathlib.Order.CompletePartialOrder import Mathlib.RingTheory.Polynomial.Resultant.Basic import Mathlib.RingTheory.SimpleRing.Principal import Mathlib.Algebra.GroupWithZero.Submonoid.CancelMulZero import Mathlib.Algebra.Module.StablyFree.Basic import Mathlib.NumberTheory.Padics.RingHoms set_option autoImplicit false open TypeDensity open Polynomial
Formal statement
theorem TypeDensity.frobenius_fraction_extension (O : Type) [CommRing O] [IsDomain O]
[IsDiscreteValuationRing O] [IsAdicComplete (IsLocalRing.maximalIdeal O) O]
[Finite (IsLocalRing.ResidueField O)] (Φ : Polynomial O) (hΦ : IsUnramifiedLift O Φ)
[IsDomain (AdjoinRoot Φ)] (ι : BaseField O →+* BaseField (AdjoinRoot Φ))
(hι : ∀ c : O, ι (algebraMap O (BaseField O) c) =
algebraMap (AdjoinRoot Φ) (BaseField (AdjoinRoot Φ)) (algebraMap O (AdjoinRoot Φ) c)) :
∃ τ : ℕ → (BaseField (AdjoinRoot Φ) ≃+* BaseField (AdjoinRoot Φ)),
(∀ (i : ℕ) (x : AdjoinRoot Φ), τ i (algebraMap (AdjoinRoot Φ) (BaseField (AdjoinRoot Φ)) x) =
algebraMap (AdjoinRoot Φ) (BaseField (AdjoinRoot Φ)) (frobeniusIter O Φ i x))
∧ (∀ (i : ℕ) (y : BaseField O), τ i (ι y) = ι y)
∧ τ 0 = RingEquiv.refl (BaseField (AdjoinRoot Φ)) ∧ (∀ i : ℕ, τ (i + 1) = (τ i).trans (τ 1))
∧ (∀ z : BaseField (AdjoinRoot Φ), τ Φ.natDegree z = z)
∧ (∀ z : BaseField (AdjoinRoot Φ), τ 1 z = z → ∃ y : BaseField O, ι y = z) := by sorrySource
TypeDensity/Unramified/DescentTypes.lean#L123-L184