Abstract

We give an elementary proof of a recent metrical Diophantine result by D. Kleinbock related to badly approximable vectors in affine subspaces.

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Audited against arXiv v2

Not a correctness certificate. A “Correct” result may include yellow typos or minor formal corrections that do not affect substantive soundness. It means this audit found no unresolved substantive error under the stated criteria; it does not replace expert scrutiny or formal verification.

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Detailed mathematical audit

Generated August 20, 2026
01Statements3 reported findingsCorrect

The metric theorem is correct under its intended finite-scaling hypotheses. Corollary 2 needs the same logarithmic parameter restriction already used in Corollary 1.

Theorem 1Correct

Metric transfer from a badly approximable subspace

Page 2 · Theorem 1 · arXiv:0906.1541v2

The covering estimate gives a cumulative lattice-point count jTζj(R)μT\sum_{j\leq T}\zeta_j^{(R)}\ll\mu_T. Partial summation against ((φ(T))/T)a((\varphi(T))/T)^a and the assumed convergence of μTλT\sum\mu_T\lambda_T make the exceptional limsup set null, proving that almost every point of AA is φ\varphi-badly approximable.

Condition (5)Typo

The scaling supremum must be finite

Page 2 · Equation (5) and Theorem 1 · arXiv:0906.1541v2

Replace supT1φ(κT)/φ(T)+\sup_{T\geq1}\varphi(\kappa T)/\varphi(T)\leq+\infty by supT1φ(T)/φ(κT)<+\sup_{T\geq1}\varphi(T)/\varphi(\kappa T)<+\infty, equivalently a positive lower bound for φ(κT)/φ(T)\varphi(\kappa T)/\varphi(T) for each fixed κ1\kappa\geq1. The printed comparison with ++\infty is vacuous, while the Borel–Cantelli reduction needs exactly this fixed-scale lower comparison when xRq|x|\leq R|q|. The surrounding analogous condition (4) and the use on page 4 determine the correction.

Corollary 2Minor formal correction

The range Δ>1/a\Delta>1/a and the exponent 1/a1/a should be displayed

Page 2 · Corollary 2 · arXiv:0906.1541v2

State Δ>1/a\Delta>1/a and define φa,Δ(T)=T1/a(logT)Δ\varphi_{a,\Delta}(T)=T^{-1/a}(\log T)^{-\Delta}. Equation (7) is written with exponent 1/d1/d for Corollary 1, so merely referring to it leaves the aa-dimensional specialization and its necessary range unstated. With this local substitution, μTλTT1(logT)aΔ\mu_T\lambda_T\asymp T^{-1}(\log T)^{-a\Delta} and the series converges exactly in the displayed range. No later statement depends on a different range.

02Proofs2 reported findingsCorrect

The lattice covering, Borel–Cantelli, and partial-summation steps are correct after the explicit scaling-notation correction.

Equation (9)Correct and complete

Covering count for integer points

Pages 2–3 · construction of ΩT\Omega_T, ΠT\Pi_T, and Equation (9) · arXiv:0906.1541v2

After ordering two lattice points by their zeroth coordinate, their difference lies in ΩT\Omega_T. Thus every translate of 12ΩT\frac12\Omega_T contains at most one lattice point. Comparing the aba-b transverse widths of ΠT\Pi_T and ΩT\Omega_T yields O((T/ψ(T))ab)=O(μT)O((T/\psi(T))^{a-b})=O(\mu_T) translates.

Borel–Cantelli reductionCorrect and complete

The exceptional sets have summable measure

Pages 3–4 · Equations (11)–(12) · arXiv:0906.1541v2

Each height-TT lattice point contributes an aa-dimensional ball of radius comparable to φ(T)/T\varphi(T)/T. Dyadic decomposition of Equation (9) gives jTζj(R)μT\sum_{j\leq T}\zeta_j^{(R)}\ll\mu_T, since monotonicity of ψ\psi supplies a geometric factor 2ν(ab)2^{-\nu(a-b)}. Abel summation then converts the series to μTλT\sum\mu_T\lambda_T, with the boundary term tending to zero.

03Novelty0 reported findingsNo non-novelty findings

No non-novelty findings.

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Paper
arXiv:0906.1541v2
Authors listed
Nikolay G. Moshchevitin
Audit date
August 20, 2026
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