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The unit loop of a finite-energy cylinder of small area with positive actions is a periodic orbit

Proved
FiniteEnergyPlane.exists_reebOrbit_loop_of_cylinder

by Mazecto · Nov 4, 2026 · Mathlib 0df444a (Lean v4.33.1)

contact-geometrypseudoholomorphic-curvessymplectic-geometry

Let S=H−1(1)S=H^{-1}(1)S=H−1(1) be a strictly star-shaped level. Let C,e,ηC,e,\etaC,e,η with e,η>0e,\eta>0e,η>0, where eee is smaller than the difference of any two distinct periods at most CCC of periodic Reeb orbits. Let www be a finite-energy J~\tilde JJ~-holomorphic curve on C∖{0}\mathbb{C}\setminus\{0\}C∖{0} with Hofer energy at most CCC, dλd\lambdadλ-energy at most eee, and action at least η\etaη on every counterclockwise circle about 000. Then there are a periodic Reeb orbit (x,T)(x,T)(x,T) with T≤CT\le CT≤C and c∈Rc\in\mathbb{R}c∈R such that proj(w(e2πit))=x(Tt+c)\mathrm{proj}(w(e^{2\pi it}))=x(Tt+c)proj(w(e2πit))=x(Tt+c) for all ttt.

Preamble
import Definitions.Def_FiniteEnergyPlane_Setting
Formal statement
namespace FiniteEnergyPlane

open MeasureTheory Metric Filter Topology
open scoped ContDiff ENNReal Real

/-- Finite-energy cylinders of small area. Let `e, η > 0`, with `e` smaller than the difference of
any two distinct periods at most `C` of periodic Reeb orbits, and let `w` be a finite-energy
`J̃`-holomorphic curve on `ℂ \ {0}` with Hofer energy at most `C`, `dλ`-energy at most `e` and action
at least `η` on every counterclockwise circle about `0`. Then there are a periodic Reeb orbit `(x, T)`
with `T ≤ C` and `c ∈ ℝ` with `proj(w(e^{2π i t})) = x(T t + c)` for all `t`. -/
theorem exists_reebOrbit_loop_of_cylinder {n : ℕ} (H : V n → ℝ) (hH : IsStrictlyStarShapedLevel H)
    (J : V n → V n →L[ℝ] V n) (hJ : IsCompatibleXiStructure H J) (w : ℂ → V n)
    (hw : IsFiniteEnergyCurve H J {z | z ≠ 0} w) (C e η : ℝ) (he : 0 < e)
    (he₂ : ∀ Q₁ Q₂ : ReebOrbit H, Q₁.T ≤ C → Q₂.T ≤ C → Q₁.T ≠ Q₂.T → e < |Q₁.T - Q₂.T|)
    (hη : 0 < η) (hE : energy H {z | z ≠ 0} w ≤ ENNReal.ofReal C)
    (hd : dlambdaEnergy H {z | z ≠ 0} w ≤ ENNReal.ofReal e)
    (hact : ∀ ρ : ℝ, 0 < ρ → η ≤ loopAction H w (ccwLoop ρ)) :
    ∃ Q : ReebOrbit H, Q.T ≤ C ∧ ∃ c : ℝ, ∀ t : ℝ,
      loopInS H w (ccwLoop 1) t = Q.x (Q.T * t + c) := by
  sorry

end FiniteEnergyPlane
Source
U. Hryniewicz, Fast finite-energy planes in symplectizations and applications, Trans. Amer. Math. Soc. 364 (2012), 1859-1931, Lemma 4.11; H. Hofer, K. Wysocki, E. Zehnder, Finite energy cylinders of small area, Ergodic Theory Dynam. Systems 22 (2002), 1451-1486, Theorem 1.1

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