OAI/Geometry/RCD/Metric/BoundedCompactApproximation.lean

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Bounded compact Lipschitz approximation in L²

  1. theorem OAI.RegularPointCoordinates.SobolevSpace.bounded_compact_L2_approximation line 18

    Source documentation

    Clip the compact recovery sequence to preserve the amplitude of the original bounded Sobolev function. L² convergence suffices after heat flow.

    theorem SobolevSpace.bounded_compact_L2_approximation (f : SobolevSpace μ hQ)
        (C : ℝ≥0) (hf : ∀ᵐ x ∂μ, |SobolevSpace.toLp μ hQ f x| ≤ C) (p : X) :
        ∃ (us : ℕ → Lp ℝ 2 μ) (gs : ℕ → X → ℝ),
          Tendsto us atTop (𝓝 (SobolevSpace.toLp μ hQ f)) ∧
          (∀ i, ∃ L : ℝ≥0, LipschitzWith L (gs i)) ∧
          (∀ i, HasCompactSupport (gs i)) ∧
          (∀ i, us i =ᵐ[μ] gs i) ∧ (∀ i x, |gs i x| ≤ C) := by
    …

    Mentions: OAI.RegularPointCoordinates.SobolevSpace, OAI.RegularPointCoordinates.SobolevSpace.toLp