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Normalized rescalings at a puncture converge to a curve with zero dλ-energy

Proved
FiniteEnergyPlane.exists_subseq_tendsto_rescaled_punctured

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

finite-energypseudoholomorphic-curvessymplectic-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. Assume the gradient bound near the puncture: there are r>0r>0r>0 and CCC with ∣z∣ ∣∇u(z)∣≤C|z|\,|\nabla u(z)|\le C∣z∣∣∇u(z)∣≤C for 0<∣z∣<r0<|z|<r0<∣z∣<r, where ∣∇u∣=∥Da∥+∥Dw∥|\nabla u|=\|Da\|+\|Dw\|∣∇u∣=∥Da∥+∥Dw∥. Let ρk→0\rho_k\to0ρk​→0 with ρk>0\rho_k>0ρk​>0. Then there are a subsequence ρkj\rho_{k_j}ρkj​​ and a finite-energy J~\tilde JJ~-holomorphic curve v:C∖{0}→R2n+2∖{0}v:\mathbb C\setminus\{0\}\to\mathbb R^{2n+2}\setminus\{0\}v:C∖{0}→R2n+2∖{0} with ∫C∖{0}v∗dλ=0\int_{\mathbb C\setminus\{0\}}v^*d\lambda=0∫C∖{0}​v∗dλ=0 such that the normalized rescalings

vj(z)=e−2a(u(ρkj)) u(ρkjz)v_j(z)=e^{-2a(u(\rho_{k_j}))}\,u(\rho_{k_j}z)vj​(z)=e−2a(u(ρkj​​))u(ρkj​​z)

converge to vvv in Cloc∞(C∖{0})C^\infty_{\mathrm{loc}}(\mathbb C\setminus\{0\})Cloc∞​(C∖{0}).

This is the puncture counterpart of exists_subseq_tendsto_rescaled_plane (rescalings of a plane at infinity); it is the blow-up step in the asymptotic analysis of a finite-energy curve at a nonremovable puncture.

Formalization Note In the coordinates y=e2axy=e^{2a}xy=e2ax (x∈Sx\in Sx∈S) of R2n+2∖{0}\mathbb R^{2n+2}\setminus\{0\}R2n+2∖{0}, multiplying by e−2a(u(ρk))e^{-2a(u(\rho_k))}e−2a(u(ρk​)) is the R\mathbb RR-translation by −a(u(ρk))-a(u(\rho_k))−a(u(ρk​)). uuu is a function on all of C\mathbb CC; only its values on ball 0 1 \ {0} matter. The rescaled maps are defined on all of C\mathbb CC and are J~\tilde JJ~-holomorphic on {0<∣z∣<1/ρk}\{0<|z|<1/\rho_k\}{0<∣z∣<1/ρk​}. Cloc∞C^\infty_{\mathrm{loc}}Cloc∞​ convergence is JHolomorphic.TendstoCInftyLocOn on {z | z ≠ 0}; the gradient bound is the hypothesis hG with gradNorm.

Preamble
import Definitions.Def_FiniteEnergyPlane_Setting
Formal statement
namespace FiniteEnergyPlane

open MeasureTheory Metric Filter Topology
open scoped ContDiff ENNReal Real

/-- Limits of the normalized rescalings at a puncture. Let `u` be a finite-energy
`J̃`-holomorphic curve on the punctured unit disc with the gradient bound
`|z| |∇u(z)| ≤ C` for `0 < |z| < r`, and let `ρ_k → 0⁺`. Then along a subsequence the maps
`z ↦ e^{-2a(u(ρ_k))} u(ρ_k z)` converge in `C^∞_loc(ℂ \ {0})` to a finite-energy
`J̃`-holomorphic curve `w` on `ℂ \ {0}` with zero `dλ`-energy. -/
theorem exists_subseq_tendsto_rescaled_punctured {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)
    (ρ : ℕ → ℝ) (hρ : ∀ k, 0 < ρ k) (hρ0 : Tendsto ρ atTop (𝓝 0)) :
    ∃ φ : ℕ → ℕ, StrictMono φ ∧ ∃ w : ℂ → V n, IsFiniteEnergyCurve H J {z | z ≠ 0} w ∧
      dlambdaEnergy H {z | z ≠ 0} w = 0 ∧
      JHolomorphic.TendstoCInftyLocOn
        (fun j z => Real.exp (-2 * aCoord H (u ((ρ (φ j) : ℝ) : ℂ))) • u (((ρ (φ j) : ℝ) : ℂ) * z))
        w {z | z ≠ 0} := by
  sorry

end FiniteEnergyPlane
Source
C. Wendl, Lectures on Symplectic Field Theory, arXiv:1612.01009, proof of Theorem 9.8; H. Hofer, Invent. Math. 114 (1993), Section 3

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