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A puncture of zero charge is removable

Proved
FiniteEnergyPlane.isRemovablePuncture_of_tendsto_loopAction_zero

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). Assume the gradient bound near the puncture and Q(ρ)→0Q(\rho)\to0Q(ρ)→0 as ρ→0+\rho\to0^+ρ→0+. Then the puncture is removable: uuu agrees on D˙\dot DD˙ with a smooth J~\tilde JJ~-holomorphic map D→R2n+2∖{0}D\to\mathbb R^{2n+2}\setminus\{0\}D→R2n+2∖{0}. (With zero charge the shifted cylinders u(e−2π(s+it))u(e^{-2\pi(s+it)})u(e−2π(s+it)) converge to constants, so aaa stays bounded near 000, uuu maps a punctured neighbourhood of 000 into a compact subset of R×S\mathbb R\times SR×S with finite Euclidean energy, and the removable singularity theorem applies.)

Preamble
import Definitions.Def_FiniteEnergyPlane_Setting
Formal statement
namespace FiniteEnergyPlane

open MeasureTheory Metric Filter Topology
open scoped ContDiff ENNReal Real

/-- (c) Zero charge: under the gradient bound, if the loop actions tend to `0` then the puncture
is removable. -/
theorem isRemovablePuncture_of_tendsto_loopAction_zero {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)
    (hG : ∃ r : ℝ, 0 < r ∧ ∃ C : ℝ, ∀ z : ℂ, z ≠ 0 → ‖z‖ < r → ‖z‖ * gradNorm H u z ≤ C)
    (hQ : Tendsto (fun ρ => loopAction H u (cwLoop 0 ρ)) (𝓝[>] 0) (𝓝 0)) :
    IsRemovablePuncture H J u 0 1 := 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 (removability when the charge vanishes); 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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