arXiv:2606.16699v1

Quantitative Oppenheim Conjecture for Random Quadratic Forms and Optimal Variance Bounds in Function Fields

Jiyoung Han, Noy Soffer Aranov

math.NTmath.DSmath.PR11H0611K3811J61

Abstract

We prove a quantitative version of Oppenheim's conjecture in the function field setting. In order to do so, we compute the higher moments of the Siegel transform. In particular, we find an optimal bound on the variance of the number of lattice points in a set. Moreover, we compute the exact variance of the number of lattice points in a ball, which is of independent interest.

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Audited against arXiv v1

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 15, 2026
01Statements3 reported findingsContains unsupported statements

The Siegel mean formula, variance bound, exact ball variance after a verified repair, shell-volume formula for ball targets, and bounded moments of the Margulis function are supported. Theorem 1.1 is not able to be verified for an arbitrary bounded measurable target because the required quantitative volume estimate is proved only for a ball.

Theorem 1.1Not able to verify

The arbitrary-measurable-target scope is not established

Page 3 · Theorem 1.1; pages 17–22 · Theorems 4.3, 4.9, and proof of Theorem 1.1 · arXiv:2606.16699v1

Theorem 1.1 allows every bounded measurable IKI\subset K_\infty. The volume theorem used in its proof, Theorem 4.3, assumes that I=a+xbOI=a+x^b\mathcal O is a one-dimensional ball. Nevertheless, estimate (4.13) invokes Theorem 4.3 for the arbitrary measurable set appearing in Theorem 4.9, and the final proof again invokes it in that scope. Approximation by finite unions of balls gives qualitative measure approximation, but for a completely arbitrary measurable set it does not automatically give the exponential accuracy needed for the stated error O(qδt(n2))O(q^{\delta t(n-2)}). No boundary regularity or quantitative approximation argument is supplied. The result for a ball, and plausibly for target classes with suitable quantitative approximation, is supported; the full measurable-set statement is not.

Full paper, version 1
Proposition 1.7Correct

The exact variance formula survives a correction to its counting step

Pages 4 and 16–17 · Proposition 1.7 and proof · arXiv:2606.16699v1

The per-polynomial count printed after (3.28) is false, but the aggregate count needed in the variance sum is correct. Writing a=Q+ba=Q+b and summing first over nonzero bb with degbdt\deg b\leq d-t, the number of monic QQ of degree dd coprime to a fixed bb of degree ee is qdeφ(b)q^{d-e}\varphi(b). Summing over bb gives (q1)q2dt(q-1)q^{2d-t}, exactly the aggregate value used in the subsequent geometric series. Thus the displayed variance formula follows after this verified reordering repair.

Full paper, version 1
Theorems 1.1 and 1.2Minor formal correction

The scale and leading-constant notation need local corrections

Pages 3 and 21–22 · Theorems 1.1–1.2 and their proofs · arXiv:2606.16699v1

Norms on KnK_\infty^n take values in qZq^{\mathbb Z}, and the shell proof sums over integer exponents, so the quantifier on tt should specify tZt\in\mathbb Z rather than all real t>tQ,It>t_{Q,I}. Also, the shell-volume coefficient is cQ=JQqn2/(qn21)c_Q=J_Qq^{n-2}/(q^{n-2}-1), while the Siegel mean contributes an additional factor qnq^n to the lattice-count coefficient in (4.14). Calling both coefficients CQC_Q creates a normalization mismatch. Distinguishing cQc_Q from CQ=qncQC_Q=q^n c_Q and restricting the scale to integer exponents are unique local corrections; neither changes the substance of the asymptotic statement.

Full paper, version 1
02Proofs2 reported findingsContains incorrect or incomplete proofs

The proof of the quantitative Oppenheim theorem uses the ball-volume theorem outside its hypotheses. The proof of the exact variance formula also contains a false individual coprimality count, although a direct aggregate recount repairs that formula.

Proof of Theorems 4.9 and 1.1Incomplete as written

The Borel–Cantelli estimate applies a ball theorem to an arbitrary measurable set

Pages 17–22 · Theorem 4.3, estimate (4.13), and proof of Theorem 1.1 · arXiv:2606.16699v1

Theorem 4.3 proves the required volume law only when II is a ball. In (4.13), the proof cites that theorem to obtain Vol(Ahi,I,t)qt(n2)\operatorname{Vol}(A_{h_i,I,t})\asymp q^{t(n-2)} for a merely measurable II, and the final proof requires the sharper leading-term formula in the same unsupported scope. Repair classification: No repair supplied for arbitrary measurable targets. Restricting Theorems 4.9 and 1.1 to ball targets is a verified scope repair; extending them further requires an explicit target-approximation theorem with a rate compatible with the claimed error.

Full paper, version 1
Proof of Proposition 1.7Incorrect as written

The individual count after (3.28) is false

Pages 16–17 · equation (3.28) and the following inclusion–exclusion calculation · arXiv:2606.16699v1

The manuscript claims that for each monic QQ of degree dtd\geq t, the count in (3.28) equals φ(Q)/qt1\varphi(Q)/q^{t-1}. If QQ is irreducible and d=t2d=t\geq2, the admissible polynomials are a=Q+ca=Q+c with cFq×c\in\mathbb F_q^\times, so the count is q1q-1, whereas the printed expression is (qd1)/qd1(q^d-1)/q^{d-1} and is not even an integer. The inclusion–exclusion step improperly assigns fractional counts when a divisor degree exceeds dtd-t. Repair classification: Verified repair. Sum first over b=aQb=a-Q as described in the statement finding; the aggregate count is (q1)q2dt(q-1)q^{2d-t} and the remainder of the variance computation is unchanged.

Full paper, version 1
03Novelty0 reported findingsNo non-novelty findings

No non-novelty findings.

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Paper
arXiv:2606.16699v1
Authors listed
Jiyoung Han, Noy Soffer Aranov
Audit date
August 15, 2026
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