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2102.04970

Contact three-manifolds with exactly two simple Reeb orbits

Dan Cristofaro-Gardiner, Umberto Hryniewicz, Michael Hutchings, Hui Liu

correctmedium confidence
Category
math.DS
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:55 AM

Audit review

The paper’s Theorem 1.2 states exactly the target claim—if a closed 3-manifold admits a contact form with exactly two simple Reeb orbits, then the form is nondegenerate and both simple orbits are irrationally elliptic—and sketches the proof via ECH spectral invariants, the Volume Property, an ECH-index stability proposition, and asymptotic optimization yielding relations (1.3)–(1.4) that force irrational ellipticity . The candidate solution follows the same route: (i) torsion of [γi] and irrationality of T1/T2 via the Volume Property (see Lemma 4.1 and the footnote explaining T1/T2 is irrational) ; (ii) an explicit asymptotic ECH-index formula for two-orbit sets (Lemma 4.5) ; (iii) a stability estimate for the ECH index under perturbations (Proposition 3.1) ; and (iv) the derivation of (1.3)–(1.4) and ensuing irrational ellipticity of both orbits, hence nondegeneracy of all iterates and of the contact form itself . The only discrepancy is notation: the paper denotes Seifert rotation numbers by φi (with θ reserved for rotation relative to a global trivialization), while the model uses θi for Seifert rotation numbers; otherwise the logic and ingredients coincide.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The paper establishes a sharp and conceptually satisfying result about Reeb dynamics with exactly two simple orbits, using powerful ECH techniques together with a novel stability estimate and a clean asymptotic optimization. The argument is coherent, technically careful, and well-situated within the literature. Minor presentational refinements (especially around rotation-number notation and heuristic guidance from the Volume Property to the key relations) would further enhance readability.