OAI/GroupTheory/PolycyclicRecognition/Geometry/BoundaryShadowDescent.lean

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Descending centered ray limits to boundary maps with compact shadows

  1. theorem OAI.PolycyclicRecognition.boundary_shadow_of_centered_limits line 16

    Source documentation

    Continuous fixed-element actions transport normalized ray limits. Asymptotic equality on the actual source fibers then gives a well-defined boundary map and the same common compact shadow.

    theorem boundary_shadow_of_centered_limits
        {G S Q : Type*} [Group G] [Group Q] [TopologicalSpace Q]
        [T2Space Q] [IsTopologicalGroup Q]
        (act : G →* Equiv.Perm Q) (hact : ∀ g, Continuous (act g))
        (q : G → S) (hq : Function.Surjective q) (F : G → G) (ray : ℕ → G)
        (K : Set Q) (k : G → Q) (hkK : ∀ x, k x ∈ K)
        (hk : ∀ x, Tendsto (fun n => act ((F x)⁻¹ * F (x * ray n)) 1)
          atTop (𝓝 (k x)))
        (hfiber : ∀ x y, q x = q y →
          Tendsto (fun n => (act (F (x * ray n)) 1)⁻¹ * act (F (y * ray n)) 1)
            atTop (𝓝 (1 : Q))) :
        ∃ B : S → Q, ∀ x,
    …