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The asymptotic winding at ∞\infty∞ is one more than the winding of π∂su\pi\partial_s uπ∂s​u along large circles

Proved
FiniteEnergyPlane.hasWindInfAt_cylInf_of_hasLoopWind

by Mazecto · Nov 3, 2026 · Mathlib 0df444a (Lean v4.33.1)

pseudoholomorphic-curvesreeb-dynamicssymplectizationwinding-numbers

Let S=H−1(1)⊂R4S=H^{-1}(1)\subset\mathbb{R}^4S=H−1(1)⊂R4 be a strictly star-shaped level, JJJ a dλ0d\lambda_0dλ0​-compatible complex structure on ξ\xiξ, and J~\tilde JJ~ the induced almost complex structure on R4∖{0}≅R×S\mathbb{R}^4\setminus\{0\}\cong\mathbb{R}\times SR4∖{0}≅R×S. Let U⊂CU\subset\mathbb{C}U⊂C be open with {z:∣z∣>R}⊂U\{z:|z|>R\}\subset U{z:∣z∣>R}⊂U, and let uuu be smooth, nonvanishing and J~\tilde JJ~-holomorphic on UUU. Suppose that the ξ\xiξ-component π ∂su\pi\,\partial_s uπ∂s​u, read in Hryniewicz's global frame of ξ\xiξ, has winding number kkk along every circle t↦ρe2πitt\mapsto\rho e^{2\pi it}t↦ρe2πit with ρ>R\rho>Rρ>R. Then in the positive cylindrical coordinates (s,t)↦e2π(s+it)(s,t)\mapsto e^{2\pi(s+it)}(s,t)↦e2π(s+it) at ∞\infty∞,

wind∞(u,∞)=k+1.\mathrm{wind}_\infty(u,\infty)=k+1 .wind∞​(u,∞)=k+1.

This expresses the asymptotic winding at the positive puncture ∞\infty∞, which is defined in cylindrical coordinates, through the winding of π∂su\pi\partial_s uπ∂s​u along large circles in the plane coordinate zzz.

Formalization Note R4\mathbb{R}^4R4 is V 1, J~\tilde JJ~ is Jtilde H J, and π∂su\pi\partial_s uπ∂s​u in the global frame is piDs H u : ℂ → ℂ. The circles are ccwLoop ρ t =ρe2πit=\rho e^{2\pi it}=ρe2πit. The conclusion is HasWindInfAt H u cylInf 1 (k + 1): for all large sss the loop t↦π∂sw(s,t)t\mapsto\pi\partial_s w(s,t)t↦π∂s​w(s,t) of w=pr∘u∘cylInfw=\mathrm{pr}\circ u\circ\mathrm{cylInf}w=pr∘u∘cylInf has winding number k+1k+1k+1. No energy bound or asymptotic hypothesis is assumed.

Preamble
import Definitions.Def_FiniteEnergyPlane_Winding
Formal statement
namespace FiniteEnergyPlane

open MeasureTheory Metric Filter Topology
open scoped ContDiff ENNReal Real

/-- Let `u` be smooth, nonvanishing and `J̃`-holomorphic on an open set `U` containing
`{z : R < ‖z‖}`, and suppose that `π ∂ₛu` (in the global frame, `piDs H u`) has winding number `k`
along every counterclockwise circle `t ↦ ρ e^{2πit}` with `ρ > R`. Then the asymptotic winding of
`u` at the positive puncture `∞` in the cylindrical coordinates `cylInf` is `k + 1`. -/
theorem hasWindInfAt_cylInf_of_hasLoopWind (H : V 1 → ℝ) (hH : IsStrictlyStarShapedLevel H)
    (J : V 1 → V 1 →L[ℝ] V 1) (hJ : IsCompatibleXiStructure H J) (U : Set ℂ) (hU : IsOpen U)
    (u : ℂ → V 1) (hu : ContDiffOn ℝ ∞ u U) (hu0 : ∀ z ∈ U, u z ≠ 0)
    (hhol : JHolomorphic.IsJHolomorphicOn (Jtilde H J) U u) (R : ℝ)
    (hRU : ∀ z : ℂ, R < ‖z‖ → z ∈ U) (k : ℤ)
    (hk : ∀ ρ > R, HasLoopWind (fun t => piDs H u (ccwLoop ρ t)) k) :
    HasWindInfAt H u cylInf 1 (k + 1) := by
  sorry

end FiniteEnergyPlane
Source
U. Hryniewicz, J. Symplectic Geom. 12 (2014), arXiv:1105.2077, Section 2.2.4 and Lemma 2.15; H. Hofer, K. Wysocki, E. Zehnder, GAFA 5 (1995)

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