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Uniform area evolution for width comparison

Definition
OpenGA_WidthAreaEvolutionData

by Xinze-Li-Moqian · Sep 10, 2026 · Mathlib 0df444a (Lean v4.33.1)

finite-extinctiongeometric-analysiswidth

Finite-energy comparison fields, a conformal limiting realizer, and time-dependent real area profiles. The energy caps converge to the initial width. For every positive error, one time interval and one sequence cutoff work for every slice: the evolved family bounds the width and each area derivative is at most −4π−RA∗/2+ε+(Aj−Aj,p)/δ-4π-R A_*/2+ε+(A_j-A_{j,p})/δ−4π−RA∗​/2+ε+(Aj​−Aj,p​)/δ, where AjA_jAj​ is the initial slice supremum. The area gap allows low-area slices to have nonnegative derivative. These are analytic data; their realization by geometric sweepouts and the uniform derivative estimate are separate open obligations.

Definition code
import Definitions.Def_OpenGA_WidthComparisonData
import Mathlib.Analysis.Calculus.Deriv.MeanValue
set_option autoImplicit false
open Set Filter
open scoped Topology

namespace OpenGA

/-- Analytic input before integrating the short-time area estimate. The same
time interval and sequence cutoff work for every slice. The derivative bound
allows slices below the initial supremum to use their initial area gap;
it does not demand negative area derivative from constant endpoint slices. -/
structure WidthAreaEvolutionData (width : ℝ → ℝ) (time scalar : ℝ) where
  realizer : FiniteEnergyPair
  realizer_conformal : realizer.IsConformal
  realized_energy : realizer.energy = width time
  competitor : ℕ → Icc (0 : ℝ) 1 → FiniteEnergyPair
  energy_cap : ℕ → ℝ
  energy_le_cap : ∀ j p, (competitor j p).energy ≤ energy_cap j
  cap_tendsto : Tendsto energy_cap atTop (𝓝 (width time))
  area : ℕ → Icc (0 : ℝ) 1 → ℝ → ℝ
  area_initial : ∀ j p, area j p time = (competitor j p).area
  uniform_evolution : ∀ ε : ℝ, 0 < ε → ∃ δ : ℝ, 0 < δ ∧ ∃ start : ℕ,
    ∀ j ≥ start,
      (∀ s ∈ Ioo time (time + δ), width s ≤ ⨆ p, area j p s) ∧
      (∀ p, ContinuousOn (area j p) (Icc time (time + δ))) ∧
      (∀ p s, s ∈ Ioo time (time + δ) → DifferentiableAt ℝ (area j p) s) ∧
      (∀ p s, s ∈ Ioo time (time + δ) →
        deriv (area j p) s ≤ -(4 * Real.pi) - scalar / 2 * realizer.area + ε +
          ((⨆ q, (competitor j q).area) - (competitor j p).area) / δ)


end OpenGA
Source
https://github.com/MathNetwork/OpenGA/blob/feat/prove2me-differential-geometry/OpenGALib/Analysis/Width/AreaEvolution.lean

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