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A nondegenerate end at a puncture z0z_0z0​, read at the puncture 000 of the unit disc

Proved
FiniteEnergyPlane.isNondegenerateEnd_comp_affine

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

pseudoholomorphic-curvesreeb-dynamicssymplectization

Let S=H−1(1)⊂R2n+2S=H^{-1}(1)\subset\mathbb{R}^{2n+2}S=H−1(1)⊂R2n+2, let P=(x,T)P=(x,T)P=(x,T) be a periodic Reeb orbit on SSS and ε∈{±1}\varepsilon\in\{\pm1\}ε∈{±1}. Let u:C→R2n+2u:\mathbb{C}\to\mathbb{R}^{2n+2}u:C→R2n+2, z0∈Cz_0\in\mathbb{C}z0​∈C and r>0r>0r>0. Suppose that in the cylindrical coordinates (s,t)↦z0+e−2π(s+it)(s,t)\mapsto z_0+e^{-2\pi(s+it)}(s,t)↦z0​+e−2π(s+it) at z0z_0z0​, uuu has a nondegenerate end over PPP with sign ε\varepsilonε (Hryniewicz, Definition 2.9 (1), (2), (4)): for some d,c∈Rd,c\in\mathbb{R}d,c∈R and b>0b>0b>0, a(s,t)−εTs−d→0a(s,t)-\varepsilon Ts-d\to0a(s,t)−εTs−d→0 and ebs(w(s,t)−x(εTt+c))→0e^{bs}\big(w(s,t)-x(\varepsilon Tt+c)\big)\to0ebs(w(s,t)−x(εTt+c))→0 uniformly in ttt as s→+∞s\to+\inftys→+∞, where aaa and www are the R\mathbb{R}R- and SSS-components of uuu. Then u~(z)=u(z0+rz)\tilde u(z)=u(z_0+rz)u~(z)=u(z0​+rz) has a nondegenerate end over the same PPP with the same sign ε\varepsilonε in the cylindrical coordinates (s,t)↦e−2π(s+it)(s,t)\mapsto e^{-2\pi(s+it)}(s,t)↦e−2π(s+it) at 000.

Together with the corresponding statement for the curve itself, this moves results about nondegenerate punctures at 000 of the unit disc to any puncture z0z_0z0​.

Formalization Note R2n+2\mathbb{R}^{2n+2}R2n+2 is V n; the nondegenerate end is IsNondegenerateEnd H u e P ε with e = cylEndAt z₀ (hypothesis) and e = cylEnd (conclusion). The constants d,c,bd,c,bd,c,b of the conclusion need not equal those of the hypothesis.

Preamble
import Definitions.Def_FiniteEnergyPlane_Winding
Formal statement
namespace FiniteEnergyPlane

open MeasureTheory Metric Filter Topology
open scoped ContDiff ENNReal Real

/-- If `u` has a nondegenerate end at the puncture `z₀` (cylindrical coordinates `cylEndAt z₀`)
over `P` with sign `ε`, then `z ↦ u (z₀ + r z)` (`r > 0`) has a nondegenerate end at `0` (cylindrical
coordinates `cylEnd`) over the same `P` with the same sign. -/
theorem isNondegenerateEnd_comp_affine {n : ℕ} (H : V n → ℝ) (u : ℂ → V n) (z₀ : ℂ) (r : ℝ)
    (hr : 0 < r) (P : ReebOrbit H) (ε : ℝ) (hnd : IsNondegenerateEnd H u (cylEndAt z₀) P ε) :
    IsNondegenerateEnd H (fun z => u (z₀ + (r : ℂ) * z)) cylEnd P ε := by
  sorry

end FiniteEnergyPlane
Source
U. Hryniewicz, J. Symplectic Geom. 12 (2014), arXiv:1105.2077, Definition 2.9 (nondegenerate punctures); standard change of coordinates

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