OAI/Geometry/RCD/Coordinates/VolumeProfileRegularity.lean

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Absolute continuity of the Euclidean-normalized volume profile

Bishop--Gromov and a positive Lipschitz comparison model make ball volume Lipschitz on every compact interval of positive radii. Multiplication by the smooth Euclidean normalization then gives the absolute continuity needed by the radial source budget.

  1. theorem OAI.RegularPointCoordinates.volume_profile_lipschitzOn line 22
  2. theorem OAI.RegularPointCoordinates.contDiff_one_comparisonModelVolume line 63

    Source documentation

    The fixed negative-curvature comparison volume is continuously differentiable.

    theorem contDiff_one_comparisonModelVolume (m : ℕ) (c : ℝ) :
        ContDiff ℝ 1 (comparisonModelVolume m c) := by
    …

    Mentions: OAI.RegularPointCoordinates.comparisonModelVolume

  3. theorem OAI.RegularPointCoordinates.ball_volume_absolutelyContinuous line 83

    Source documentation

    Ball volume is absolutely continuous away from radius zero under the published Bishop--Gromov comparison with the explicit model.

    theorem ball_volume_absolutelyContinuous {μ : Measure X} (m : ℕ) {c : ℝ} (hc : 0 ≤ c)
        (hBG : BallVolumeComparison μ (comparisonModelVolume m c)) (x : X)
        {a b : ℝ} (ha : 0 < a) (hab : a ≤ b) (hfin : μ (ball x b) ≠ ∞) :
        AbsolutelyContinuousOnInterval (fun t => μ.real (ball x t)) a b := by
    …

    Mentions: OAI.RegularPointCoordinates.BallVolumeComparison, OAI.RegularPointCoordinates.comparisonModelVolume

  4. theorem OAI.RegularPointCoordinates.normalized_ball_volume_absolutelyContinuous line 110

    Source documentation

    Euclidean-normalized volume retains absolute continuity on positive radius intervals; this does not assume monotonicity of that normalization.

    theorem normalized_ball_volume_absolutelyContinuous {μ : Measure X} (m : ℕ) {c : ℝ} (hc : 0 ≤ c)
        (hBG : BallVolumeComparison μ (comparisonModelVolume m c)) (x : X)
        {a b : ℝ} (ha : 0 < a) (hab : a ≤ b) (hfin : μ (ball x b) ≠ ∞) :
        AbsolutelyContinuousOnInterval (fun t => μ.real (ball x t) / t ^ (m + 1)) a b := by
    …

    Mentions: OAI.RegularPointCoordinates.BallVolumeComparison, OAI.RegularPointCoordinates.comparisonModelVolume

  5. theorem OAI.RegularPointCoordinates.sphere_measure_zero_of_comparison line 129

    Source documentation

    Bishop--Gromov with a positive continuous model excludes mass on every positive-radius sphere, not merely almost every sphere.

    theorem sphere_measure_zero_of_comparison {model : ℝ → ℝ}
        (hBG : BallVolumeComparison μ model) (hcont : Continuous model)
        (x : X) {r : ℝ} (hr : 0 < r) (hmodel : 0 < model r) : μ (sphere x r) = 0 := by
    …

    Mentions: OAI.RegularPointCoordinates.BallVolumeComparison