OAI/GroupTheory/PolycyclicRecognition/Algebra/ComplexCharacterLift.lean

GitHub source file

3 declarations, 0 contain sorry, 0 declared as axioms

Additive lifts of complex characters

Rotational diagonal characters in a simply connected solvable group have continuous logarithms. Uniqueness of covering lifts makes the normalized logarithm additive; its value on an exponential curve is the prescribed linear weight, with no choice of a global principal logarithm.

  1. theorem OAI.PolycyclicRecognition.eq_of_continuous_complex_exp_eq line 21

    Source documentation

    Two continuous lifts through the complex exponential agree everywhere when they agree at one point of a connected domain.

    theorem eq_of_continuous_complex_exp_eq
        {X : Type*} [TopologicalSpace X] [PreconnectedSpace X]
        {f g : X → ℂ} (hf : Continuous f) (hg : Continuous g)
        (he : ∀ x, Complex.exp (f x) = Complex.exp (g x))
        (x₀ : X) (h₀ : f x₀ = g x₀) : f = g := by
    …
  2. theorem OAI.PolycyclicRecognition.exists_additive_lift_complex_character line 32

    Source documentation

    A continuous character into the nonzero complex numbers has a normalized additive lift on a simply connected group.

    theorem exists_additive_lift_complex_character
        {G : Type*} [Group G] [TopologicalSpace G] [IsTopologicalGroup G]
        [SimplyConnectedSpace G] [LocallyPathConnectedSpace G]
        (χ : G →* ℂˣ) (hχ : Continuous (fun g => (χ g : ℂ))) :
        ∃ π : G →* Multiplicative ℂ, Continuous (fun g => (π g).toAdd) ∧
          ∀ g, Complex.exp (π g).toAdd = (χ g : ℂ) := by
    …
  3. theorem OAI.PolycyclicRecognition.additive_lift_complex_character_on_curve line 59

    Source documentation

    The additive lift recovers the exact weight along a continuous one-parameter curve starting at the identity.

    theorem additive_lift_complex_character_on_curve
        {G : Type*} [Group G] [TopologicalSpace G]
        (χ : G →* ℂˣ) (π : G →* Multiplicative ℂ)
        (hπ : Continuous (fun g => (π g).toAdd))
        (he : ∀ g, Complex.exp (π g).toAdd = (χ g : ℂ))
        (γ : ℝ → G) (hγ : Continuous γ) (hγ0 : γ 0 = 1)
        (z : ℂ) (hz : ∀ t, (χ (γ t) : ℂ) = Complex.exp ((t : ℂ) * z)) :
        ∀ t, (π (γ t)).toAdd = (t : ℂ) * z := by
    …