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Finite-order bounds of the height on the lower cut θ=−r\theta=-rθ=−r

Proved
OAI.SmoothLocal.Pulse.exists_actual_finite_lower_cut_bound_at_radius

by wurtle · Nov 4, 2026 · Mathlib 0df444a (Lean v4.33.1)

differential-geometryisometric-immersion

Notation. S=[−3,3]2S=[-3,3]^2S=[−3,3]2 is the model square; a metric is a smooth positive matrix field ggg; zzz is a scalar height; H=∇g2zH=\nabla_g^2zH=∇g2​z is its covariant Hessian; KgK_gKg​ is the Gaussian curvature; E=det⁡g (1−∣dz∣g2)E=\det g\,(1-|dz|_g^2)E=detg(1−∣dz∣g2​); q=Hxy/Hyyq=H_{xy}/H_{yy}q=Hxy​/Hyy​ is the Hessian quotient; κ(x2−h(y))\kappa(x^2-h(y))κ(x2−h(y)) is the model curvature; the patch box and the central box are the squares [−1/10,1/10]2[-1/10,1/10]^2[−1/10,1/10]2 and [−1/5,1/5]2[-1/5,1/5]^2[−1/5,1/5]2; the sheared coordinates are ξ=x, θ=y+q0x\xi=x,\ \theta=y+q_0xξ=x, θ=y+q0​x, with sheared height zsz_szs​; LLL and v∗v_*v∗​ are the class width and speed of (4.2); g~τ\tilde g_\taug~​τ​ is the test metric (4.12) built from g∗g_*g∗​; a bounded admissible height of bound MMM is an admissible height with (4.1).

Let g∗g_*g∗​ be smooth and positive on an open V⊇SV\supseteq SV⊇S and fix G,Z,d,c,e0,κ,q0,L,rG,Z,d,c,e_0,\kappa,q_0,L,rG,Z,d,c,e0​,κ,q0​,L,r with ∣q0∣≤1/20|q_0|\le1/20∣q0​∣≤1/20, 0<r<1/20<r<1/20<r<1/2, Lr≤1/20Lr\le1/20Lr≤1/20 and rrr small. For each order nnn there is C≥0C\ge0C≥0 such that for all NNN and δ>0\delta>0δ>0, for all sufficiently large τ\tauτ, the following holds for every metric gτg_\taugτ​ with C4C^4C4 bound GGG and ∣det⁡gτ∣≥d|\det g_\tau|\ge d∣detgτ​∣≥d on SSS, every cap-induction height zzz and cap-induction flow YYY for gτg_\taugτ​ with ∣q(0)−q0∣≤1/(100L)|q(0)-q_0|\le1/(100L)∣q(0)−q0​∣≤1/(100L), whenever gτg_\taugτ​ is within τ−τ\tau^{-\tau}τ−τ in Cτ(S)C^\tau(S)Cτ(S) of the test metric g~τ\tilde g_\taug~​τ​: every coordinate derivative of order at most nnn of zzz at the sheared point (x,−r)(x,-r)(x,−r), ∣x∣≤Lr|x|\le Lr∣x∣≤Lr, is bounded by CCC.

Formalization Note. This is the upstream Lean declaration OAI.SmoothLocal.Pulse.exists_actual_finite_lower_cut_bound_at_radius in lean/OAI/Geometry/IsometricImmersion/Estimates/FixedRadiusCutBounds.lean, stated verbatim; the Lean statement is authoritative for the precise hypotheses. It is an intermediate result of OpenAI's formalization.

Preamble
import Mathlib
import Definitions.Def_IsometricImmersion
import Definitions.Def_SmoothLocalIsometricSupport

namespace OAI

noncomputable section
open Set Filter Function
open scoped ContDiff Topology BigOperators

namespace SmoothLocal.Pulse
open SmoothLocal.Geometry SmoothLocal.Flow SmoothLocal.ODE SmoothLocal.Weighted
open SmoothLocal.HighEquation SmoothLocal.Analytic

Formal statement
theorem exists_actual_finite_lower_cut_bound_at_radius
    {gStar : MetricField} {V : Set Coord}
    (hgStar : SmoothPositiveOn gStar V) (hV : IsOpen V) (hSV : modelSquare ⊆ V)
    {G Z d c e0 kappa q0 L r : ℝ}
    (hG : 0 ≤ G) (hZ : 0 ≤ Z) (hd : 0 < d) (hc : 0 < c)
    (hL : 0 < L) (hq0 : |q0| ≤ 1/20) (hr : 0 < r) (hrhalf : r < 1/2)
    (hLr : L*r ≤ 1/20)
    (hrsmall : heightQuotientJetBound G Z d c*(r+107*(L*r)/100) ≤ 9/(100*L))
    (n : ℕ) :
    ∃ C : ℝ, 0 ≤ C ∧ ∀ N : ℕ, ∀ delta : ℝ, 0 < delta →
      ∀ᶠ tau : ℕ in atTop,
        ∀ (gTau : MetricField) (U W : Set Coord) (z : Coord → ℝ) (Y : ℝ → ℝ → ℝ),
          SmoothPositiveOn gTau U → IsOpen U →
          (∀ i j : Fin 2, ∀ k ≤ 4, ∀ p ∈ modelSquare,
            ‖iteratedFDeriv ℝ k (fun q => gTau q i j) p‖ ≤ G) →
          (∀ p ∈ modelSquare, d ≤ |(gTau p).det|) →
          CapInductionHeight gTau U Z c e0 z →
          CapInductionFlow gTau U G Z d c e0 kappa z Y W →
          |hessianQuotient gTau z 0-q0| ≤ 1/(100*L) →
          (∀ i j : Fin 2, ∀ k ≤ tau, ∀ p ∈ modelSquare,
            ‖iteratedFDeriv ℝ k (fun q => gTau q i j-
              testMetric gStar q0 (L*r/16) N delta (tau : ℝ) q i j) p‖ ≤
                metricApproximationAccuracy tau) →
          ∀ ds : List (Fin 2), ds.length ≤ n → ∀ x : ℝ, |x| ≤ L*r →
            |iteratedCoordPartial ds z (inverseShearCoordinates q0 (boxPoint x (-r)))| ≤ C := by
  sorry

end SmoothLocal.Pulse
end
end OAI
Source
OpenAI, A Smooth Metric with No Local Isometric Immersion into Three-Space, September 24, 2026, https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/preprints/A-Smooth-Metric-with-No-Local-Isometric-Immersion-into-Three-Space-September-24-2026/paper.pdf; Lean: openai/math at adc7f1241b42e322a6451854ab7e4b4c146bf78a, lean/OAI/Geometry/IsometricImmersion/ (Apache License 2.0), file lean/OAI/Geometry/IsometricImmersion/Estimates/FixedRadiusCutBounds.lean; Section 4.2, proof of Lemma 4.1

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