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Gradient bound near a puncture of a finite-energy curve

Proved
FiniteEnergyPlane.exists_norm_mul_gradNorm_le_near_puncture

by Alien60 · Oct 26, 2026 · Mathlib 0df444a (Lean v4.33.1)

finite-energypseudoholomorphic-curvesreeb-dynamicssymplectic-geometry

Let S=H−1(1)⊂R2n+2S=H^{-1}(1)\subset\mathbb R^{2n+2}S=H−1(1)⊂R2n+2 be a strictly star-shaped level with contact form λ=λ0∣S\lambda=\lambda_0|_Sλ=λ0​∣S​ and dλd\lambdadλ-compatible complex structure JJJ on ξ\xiξ, and let u=(a,w):D˙=D∖{0}→R×S≅R2n+2∖{0}u=(a,w):\dot D=D\setminus\{0\}\to\mathbb R\times S\cong\mathbb R^{2n+2}\setminus\{0\}u=(a,w):D˙=D∖{0}→R×S≅R2n+2∖{0} be a finite-energy J~\tilde JJ~-holomorphic curve on the punctured unit disc. Write Q(ρ)=∫01w(γρ(t))∗λQ(\rho)=\int_0^1 w(\gamma_\rho(t))^*\lambdaQ(ρ)=∫01​w(γρ​(t))∗λ for the action of the clockwise loop γρ(t)=ρe−2πit\gamma_\rho(t)=\rho e^{-2\pi i t}γρ​(t)=ρe−2πit, and call ∣z∣ ∣∇u(z)∣≤C|z|\,|\nabla u(z)|\le C∣z∣∣∇u(z)∣≤C for 0<∣z∣<r0<|z|<r0<∣z∣<r the gradient bound near the puncture, where ∣∇u∣=∥Da∥+∥Dw∥|\nabla u|=\|Da\|+\|Dw\|∣∇u∣=∥Da∥+∥Dw∥ (R\mathbb RR-invariant). Then there are r>0r>0r>0 and CCC with ∣z∣ ∣∇u(z)∣≤C|z|\,|\nabla u(z)|\le C∣z∣∣∇u(z)∣≤C for all 0<∣z∣<r0<|z|<r0<∣z∣<r. Otherwise there are zk→0z_k\to0zk​→0 with ∣zk∣ ∣∇u(zk)∣→∞|z_k|\,|\nabla u(z_k)|\to\infty∣zk​∣∣∇u(zk​)∣→∞; rescaling uk(ζ)=u(∣zk∣ζ)u_k(\zeta)=u(|z_k|\zeta)uk​(ζ)=u(∣zk​∣ζ) on 0<∣ζ∣<1/∣zk∣0<|\zeta|<1/|z_k|0<∣ζ∣<1/∣zk​∣ and bubbling off near ζk=zk/∣zk∣\zeta_k=z_k/|z_k|ζk​=zk​/∣zk​∣ (Hofer's lemma) gives a nonconstant finite-energy plane vvv whose dλd\lambdadλ-energy on each disc Bρ(0)B_\rho(0)Bρ​(0) is bounded by the liminf of the dλd\lambdadλ-energies of uuu on discs contained in B2∣zk∣(0)∖{0}B_{2|z_k|}(0)\setminus\{0\}B2∣zk​∣​(0)∖{0}. These tend to 000 because ∫D˙w∗dλ≤E(u)<∞\int_{\dot D}w^*d\lambda\le E(u)<\infty∫D˙​w∗dλ≤E(u)<∞, so ∫Cv∗dλ=0\int_{\mathbb C}v^*d\lambda=0∫C​v∗dλ=0, contradicting the positivity of the dλd\lambdadλ-energy of nonconstant finite-energy planes.

Preamble
import Definitions.Def_FiniteEnergyPlane_Setting
Formal statement
namespace FiniteEnergyPlane

open MeasureTheory Metric Filter Topology
open scoped ContDiff ENNReal Real

/-- (b) Gradient bound near a puncture: `|z| · |∇u(z)| ≤ C` near `0` (bubbling off would produce a
nonconstant finite-energy plane whose positive `dλ`-energy is captured in arbitrarily small
punctured discs about `0`). -/
theorem exists_norm_mul_gradNorm_le_near_puncture {n : ℕ} (H : V n → ℝ)
    (hH : IsStrictlyStarShapedLevel H) (J : V n → V n →L[ℝ] V n)
    (hJ : IsCompatibleXiStructure H J) (u : ℂ → V n)
    (hu : IsFiniteEnergyCurve H J (ball 0 1 \ {0}) u) :
    ∃ r : ℝ, 0 < r ∧ ∃ C : ℝ, ∀ z : ℂ, z ≠ 0 → ‖z‖ < r → ‖z‖ * gradNorm H u z ≤ C := by
  sorry

end FiniteEnergyPlane
Source
H. Hofer, Pseudoholomorphic curves in symplectizations with applications to the Weinstein conjecture in dimension three, Invent. Math. 114 (1993), 515-563, Section 3 (gradient bound near punctures, via bubbling off); C. Wendl, Lectures on Symplectic Field Theory, arXiv:1612.01009, https://arxiv.org/abs/1612.01009, Theorem 9.8 and its proof, pp. 157-160

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