2209.11862
Pairs of saddle connections of typical flat surfaces on fixed affine orbifolds.
Etienne Bonnafoux
correctmedium confidence
- Category
- Not specified
- Journal tier
- Specialist/Solid
- Processed
- Sep 28, 2025, 12:56 AM
- arXiv Links
- Abstract ↗PDF ↗
Audit review
The uploaded paper proves, for any ergodic SL(2,R)-invariant probability measure µ on a connected component H, that NA(ω,R)/R^2 converges to a finite constant cµ(A) for µ-a.e. ω (Theorem 1.2), by extending L^{2+κ} integrability of Siegel–Veech transforms to arbitrary invariant measures (Theorem 1.4) and applying Nevo’s ergodic theorem to circle averages At f̂, together with a careful trapezoid decomposition and o(e^{2t}) error control; see the stated results and proof roadmap in Sections 1.3–1.4 and 3–4 of the paper . By contrast, the model’s solution sketches an Eskin–Masur-style KAK averaging with an exponentially weighted time integral and invokes “Birkhoff’s theorem” to pass to the limit. This key step is not justified: Birkhoff’s theorem applies to Cesàro averages, not to the exponentially weighted Abel-type averages used by the model. The needed convergence is established in the paper via Nevo’s theorem for K-finite functions and circle averages, not by a direct Birkhoff argument . The model also assumes, without proof, a two-sided “pair counting identity” linking the time-averaged pair transform to NA(ω,R) with O(e^T) error; the paper instead derives a precise difference formula with explicit main and error terms on carefully chosen fibered trapezoids and bounds each error to o(e^{2t}) . While most high-level ingredients in the model’s outline match those in the paper (pair Siegel–Veech measure, smoothing/approximation, quadratic normalization), the argument as written has a critical gap in the limit passage and omits the essential K-finiteness/Nevo input and the error analysis framework that the paper supplies.
Referee report (LaTeX)
\textbf{Recommendation:} minor revisions \textbf{Journal Tier:} specialist/solid \textbf{Justification:} The paper generalizes a recent pair-counting result from Masur–Veech to arbitrary invariant measures by providing new L\^{2+κ} integrability of Siegel–Veech transforms and adapting the renormalization argument using Nevo’s theorem. The results are correct and of interest to specialists in Teichmüller dynamics and flat surfaces. Minor revisions could further clarify technical steps and normalizations.