Module

FieldFrobeniusFactorization.lean

Nyll.EtaleFundamentalGroups.FiniteEtale.FiniteField.FieldFrobeniusFactorization
2 declarations indexed from sourceView source ↗

Field Frobenius Factorization

A single Frobenius power sends every element of a finite purely inseparable extension into the original field.

Imports2
  • Mathlib.FieldTheory.PurelyInseparable.Basic
  • Mathlib.LinearAlgebra.FiniteDimensional.Basic
Imported by2

Declarations

EtaleFundamentalGroups.exists_uniform_purelyInseparable_exponent

A single Frobenius power sends every element of a finite purely inseparable extension into the original field.

Source context 7 commands

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

noncomputable section
open scoped BigOperators
universe u
namespace EtaleFundamentalGroups
variable (k L : Type u) [Field k] [Field L] [Algebra k L]
variable [IsPurelyInseparable k L] [FiniteDimensional k L]
variable (p : ℕ) [ExpChar k p] [ExpChar L p]
theorem exists_uniform_purelyInseparable_exponent :
    ∃ n : ℕ, ∀ x : L, x ^ p ^ n ∈ (algebraMap k L).range
EtaleFundamentalGroups.exists_purelyInseparable_frobenius_factorization

The Frobenius power factors in both directions through the original field.

Source context 7 commands

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

noncomputable section
open scoped BigOperators
universe u
namespace EtaleFundamentalGroups
variable (k L : Type u) [Field k] [Field L] [Algebra k L]
variable [IsPurelyInseparable k L] [FiniteDimensional k L]
variable (p : ℕ) [ExpChar k p] [ExpChar L p]
theorem exists_purelyInseparable_frobenius_factorization :
    ∃ (n : ℕ) (σ : L →+* k),
      (algebraMap k L).comp σ = iterateFrobenius L p n ∧
        σ.comp (algebraMap k L) = iterateFrobenius k p n