arXiv:2610.16605v2
Abstract
A set of positive integers is -large if every two-coloring contains arbitrarily long monochromatic arithmetic progressions with common difference in . We prove that every such set meets every nil-Bohr neighborhood of . This proves a conjecture of the first author and gives a sharp answer to a question of Host, Kra, and Maass. We also show that, for every fixed nil-Bohr neighborhood of and every , restricting the common difference to increases the extremal number for -term arithmetic progressions by at most a factor of , provided is sufficiently large.
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Detailed mathematical audit
01Statements2 reported findingsNo statement issues found
The shell-coloring theorem and its nil-Bohr recurrence and density consequences are supported for the stated weighted polynomial configurations.
Every two-coloring produces the required monochromatic weighted configuration
PDF pp. 3–4 and 8–15 · Theorem 1.9 · arXiv:2610.16605v2
The weighted polynomial matrix class is stable under the prescribed operations. Compactness of the normalized curve family and the interpolation lemma produce a uniformly controlled parameter, while the leading-coefficient and last-column lemmas decode the resulting matrix relation into exactly the configuration stated in the theorem.
Nil-Bohr recurrence and density follow from the coloring theorem
PDF pp. 2–5 and 15–16 · arXiv:2610.16605v2
Coloring successive shells in a nilmanifold converts Theorem 1.9 into a return-time statement for every neighborhood of the identity. The Følner averaging argument then yields the asserted positive-density recurrence, and the displayed specialization gives the corollary.
02Proofs2 reported findingsNo proof issues found
The rounding, compactness, interpolation, coefficient-control, and decoding arguments supporting the central coloring theorem are correct and complete.
Rounding preserves the weighted filtration and interpolation is uniform
PDF pp. 8–12 · arXiv:2610.16605v2
The rounding error lands in strictly higher weighted degree, so it cannot change the leading data used later. Compactness of the normalized curve family makes the interpolation constants uniform and supplies the finite choice needed by the shell argument.
The coefficient and last-column calculations close the construction
PDF pp. 12–15 · arXiv:2610.16605v2
The induction isolates the leading weighted coefficients with the asserted nonvanishing and divisibility properties. Reading the last matrix column then gives the desired shifts with all indices and parameter ranges matching Theorem 1.9.
03Novelty0 reported findingsNo novelty concerns found
No non-novelty findings.