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2403.05107

A CONVERSE OF DYNAMICAL MORDELL–LANG CONJECTURE IN POSITIVE CHARACTERISTIC

Jungin Lee, Gyeonghyeon Nam

correctmedium confidence
Category
Not specified
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper’s main theorem explicitly proves that any subset of N0 that is a finite union of arithmetic progressions and p-sets is an Fp(t)-DML set over a split torus (Theorem 1.6) and reduces the proof to a special case (Theorem 3.1) using Lemmas 2.1–2.3; arithmetic progressions are handled by Lemma 2.2, and closure under unions, scalings, and translations by Lemmas 2.1 and 2.3. The special case is then proved by decomposing into p-sets to which the Corvaja–Ghioca–Scanlon–Zannier bound applies, combined via an induction with Lemma 3.4; field change to Fp(t) is handled by Lemma 3.2. These steps are present and coherent in the PDF (Theorem 1.6, Lemmas 2.1–2.3, Theorem 3.1, Lemma 3.4, and the use of [CGSZ] in Theorem 1.5) . By contrast, the model’s solution misstates the small-coefficient condition needed for the CGSZ realization (it claims a threshold ∑cj ≤ q−1 via a “no-carry” normalization, whereas the paper correctly uses the stricter ∑cj < q/2 bound), and attributes a base-q digit carry argument to Lee–Nam that is not how the paper proceeds; it also overstates that all maps used are monomial endomorphisms. Hence, while the high-level structure aligns, the model’s core normalization step and citation of the threshold are incorrect.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The paper proves a clean and useful converse direction to the positive-characteristic DML framework: every finite union of arithmetic progressions and p-sets arises as a DML set over a split torus defined over Fp(t). The argument is crisp: a reduction to a special form, a careful induction supported by a key lemma, and a judicious application of a result of Corvaja–Ghioca–Scanlon–Zannier, with an appropriate field-extension lemma to pass to Fp(t). The result consolidates and streamlines known structures for DML in positive characteristic and should be of interest to researchers in arithmetic dynamics and Diophantine geometry. Minor clarifications would improve readability (e.g., explicitly flagging where K≠F2 is used, and adding a high-level overview of the induction in Section 3).