arXiv:2601.21209v2

Positive characteristic analogues of finite algebraic numbers

Daichi Matsuzuki, Honami Sakamoto, Jun Ueki

math.NT11R5811B3711R4511A0711B3911J93

Abstract

J.~Rosen introduced the ring PA0\mathcal{P}^0_{\mathcal{A}} of so-called finite algebraic numbers, which may be seen as an analogue of certain periods in the ring A=pZ/pZ/pZ/pZ\mathcal{A}=\prod_p \mathbb{Z}/p\mathbb{Z} /\bigoplus_p \mathbb{Z}/p\mathbb{Z}, pp running through all prime numbers. In this article, we introduce its positive characteristic analogue PAK0\mathcal{P}^0_{\mathcal{A}_K} over the rational function field K=Fq(θ)K=\mathbb{F}_q(θ), qq being a prime power, and study foundational properties, and provide further scopes.

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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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Generated August 15, 2026
01Statements3 reported findingsCorrect

The Frobenius-evaluation characterization, algebra and proper-inclusion results, Frobenian-set and polynomial-root consequences, density supremum, and Artin-motive period statement are supported. The characteristic-two construction used for the density theorem needs an omitted prime choice, but that choice gives a complete verified repair without changing the theorem.

Theorems 1.13, 1.16, Corollary 1.19, and Theorem 1.20Correct

Foundational characterization and algebraic consequences

Pages 4–14 · Theorems 1.13, 1.16, Corollary 1.19, Theorem 1.20, and proofs · arXiv:2601.21209v2

The equivalence between separable recurrence data, conjugation-equivariant Frobenius evaluation, and matrix coefficients is established by diagonalizing the recurrence over a finite Galois extension and applying additive and multiplicative Galois descent. Closure under sums and products follows after passing to a common Galois extension. The explicit idempotent and inseparable constructions separate all four inclusions. Chebotarev applied to the identity conjugacy class gives the KK-rational root in Theorem 1.20, and characteristic functions of conjugacy-stable subsets give the Frobenian-set converse.

Full paper, version 2
Theorem 1.21Correct

The density supremum is correct after repairing the characteristic-two wreath extension

Pages 14–17 · Lemmas 7.3–7.6 and proof of Theorem 1.21 · arXiv:2601.21209v2

Lemmas 7.3–7.5 convert the two prime densities into proportions of subsets of a finite Galois group and show that wreath extensions make the smaller proportion approach the larger one. In characteristic two, choose a prime of KK that splits completely in a Galois closure containing the Hilbert class field of LL, and let ϑ\vartheta generate one resulting principal prime of LL. The conjugate prime ideals are then distinct. In any nonzero F2\mathbb{F}_2-linear combination of the elements σ(ϑ(2i1))\sigma(\vartheta^{-(2i-1)}), a conjugate valuation sees a unique largest odd pole order, whereas every negative valuation of x2+xx^2+x is even. This proves the required Artin–Schreier independence and supplies the stated wreath extension. With that verified repair, the limiting group-count argument proves both assertions of Theorem 1.21.

Full paper, version 2
Proposition 8.2Correct

Artin tt-motive periods generate the separable closure

Pages 17–18 · Proposition 8.2 · arXiv:2601.21209v2

For a finite Galois extension L/KL/K, the matrix of Galois conjugates of a KK-basis is invertible by nondegeneracy of the trace form and satisfies the required Frobenius matrix relation. Its transpose is therefore a rigid analytic trivialization. The period matrix is the Frobenius of its inverse; its entries generate the same field as the Frobenius matrix itself, and the relation Ψ=τ(Ψ)Φ1\Psi=\tau(\Psi)\Phi^{-1} recovers every chosen basis element. Taking a basis containing an arbitrary aKsepa\in K^{\mathrm{sep}} proves the converse inclusion, while the forward inclusion is immediate from the defining matrices over finite separable extensions.

Full paper, version 2
02Proofs2 reported findingsContains incorrect or incomplete proofs

The principal arguments are complete except for the characteristic-two branch of Lemma 7.6, where distinctness is substituted for linear independence and conjugate prime ideals are not controlled. A split-prime choice gives a rigorous repair. One contradictory preimage identity in the final group argument is a removable notation error.

Lemma 7.6, characteristic twoIncomplete as written

The claimed Artin–Schreier independence does not follow from the chosen element

Pages 15–16 · characteristic-two branch of Lemma 7.6 · arXiv:2601.21209v2

The proof chooses any principal-prime generator ϑ\vartheta, shows only that ϑ(2j1)ϑ(2i1)\vartheta^{-(2j-1)}-\vartheta^{-(2i-1)} is not in the image of xx2+xx\mapsto x^2+x, and then declares the entire tuple (σ(ϑ(2i1)))σ,i(\sigma(\vartheta^{-(2i-1)}))_{\sigma,i} linearly independent in L/(x2+x)LL/(x^2+x)L. Pairwise distinct cosets do not imply linear independence, and if a nontrivial σ\sigma fixes the chosen prime then conjugate entries may repeat. Repair classification: Verified repair. Choose the base prime to split completely in a Galois closure containing the Hilbert class field, so all conjugate prime ideals are distinct and principal. At a prime supporting a nonempty linear combination, the largest occurring pole has odd order, while an element x2+xx^2+x has even negative valuation. This proves independence of the full tuple and the rest of the Kummer-style splitting argument goes through.

Full paper, version 2
Proof of Theorem 1.21Typo

The displayed identity S2=π1(S2)S'_2=\pi^{-1}(S_2) should be deleted

Page 17 · proof of Theorem 1.21, paragraph applying Lemmas 7.5–7.6 · arXiv:2601.21209v2

For ξΓ\xi\in\Gamma', the image π(CΓ(ξ))\pi(C_{\Gamma'}(\xi)) can be strictly smaller than CΓ(π(ξ))C_\Gamma(\pi(\xi)), so the newly defined set S2S'_2 is not generally π1(S2)\pi^{-1}(S_2). Indeed, making this centralizer image smaller is exactly the mechanism used in the next sentence to enlarge S2S'_2 toward S1S'_1. Deleting the equality with π1(S2)\pi^{-1}(S_2) is the unique local correction; the definition of S2S'_2, Lemma 7.5, and all subsequent inequalities then agree and the argument is unchanged.

Full paper, version 2
03Novelty0 reported findingsNo non-novelty findings

No non-novelty findings.

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Paper
arXiv:2601.21209v2
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Daichi Matsuzuki, Honami Sakamoto, Jun Ueki
Audit date
August 15, 2026
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