arXiv:2610.27640v1
Abstract
We construct a cut-and-project set in a totally irrational plane in , with a compact window which is the closure of its interior and has countable boundary, which is not bi-Lipschitz equivalent to a lattice. This answers a question of Burago and Kleiner about cut-and-project sets, and shows in particular that the hypothesis of boundary measure zero is not enough to guarantee bi-Lipschitz equivalence to a lattice. Since our set has uniform density, it also shows that a non-rectifiable Delone set need not encode a non-realisable density, answering a question of Bhat and Dymond.
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Detailed mathematical audit
01Statements2 reported findingsNo statement issues found
The construction of a regular cut-and-project Delone set with countable window boundary that is not bi-Lipschitz equivalent to a lattice, and its uniform-density consequence, are supported.
The constructed regular model set is non-rectifiable
PDF pp. 2–3 and 6–25 · arXiv:2610.27640v1
The nested interval construction makes rationally independent and produces a compact window that is the closure of its interior with countable boundary. The final boundary translation avoids every lattice internal coordinate. At each prescribed bi-Lipschitz scale, the associated strip pattern realizes the finite stretched-pair obstruction, so no bi-Lipschitz equivalence to any lattice can exist.
The example nevertheless has uniform asymptotic density
PDF pp. 4 and 17–19 · arXiv:2610.27640v1
The row-counting lemma is uniform in the square's position and compares the number of selected lattice points with the window length. After the linear identification with the physical plane, the density is . Hence every encoded limiting density is constant and therefore realizable.
02Proofs2 reported findingsNo proof issues found
The reduction to a subset of , finite-scale stretched-pair obstruction, uniform counting estimates, nested strip construction, and final boundary avoidance are correct and complete.
The finite configurations obstruct every prescribed bi-Lipschitz constant
PDF pp. 8–16 · Sections 3–4 · arXiv:2610.27640v1
The stretched-pair lemma converts the alternating adjacent-square count contrast into a quantitative separation distortion. Compactness of normalized Delone configurations turns the planar statement into a finite-scale obstruction with constants uniform over the required covering-radius class.
The stages do not interfere and the limiting window has the claimed topology
PDF pp. 17–25 · Sections 5–6 · arXiv:2610.27640v1
Previously built patterns are controlled by the uniform row estimate, while later additions occupy intervals of total length smaller than the active contrast scale. The nested choices converge to a totally irrational slope; the endpoints accumulate only at the designated countable set, and the final translation simultaneously avoids all lattice internal coordinates.
03Novelty0 reported findingsNo novelty concerns found
No non-novelty findings.