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2504.01563

Height arguments toward the dynamical Mordell–Lang problem in arbitrary characteristic

Junyi Xie, She Yang

correcthigh confidence
Category
math.DS
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper’s Theorem 1.1 proves that for a surjective endomorphism f of a projective variety X over an algebraically closed field, if every cohomological Lyapunov exponent µ_i(f) avoids Root = {a^{1/n} : a,n ∈ Z_{>0}}, then for any curve C and any point x with Of(x) = X, the intersection Of(x) ∩ C(K) is finite; see the statement and discussion around Theorem 1.1 and Remark 1.2 . The proof relies on height arguments, an Albanese reduction, and key linear-algebraic properties of cohomological Lyapunov exponents (notably µ_i(f^n) = µ_i(f)^n, Proposition 2.1(ii)) and structural steps in Proposition 3.6 and the Albanese argument in the proof of Theorem 1.1 . The model’s solution correctly notes µ_i(f^m)=µ_i(f)^m and that µ_i(f)∉Root implies µ_i(f^m)∉Z for all m, then cites the same theorem to conclude finiteness; this is logically sound and uses a condition equivalent to the paper’s hypothesis, since µ∈Root iff some power µ^m∈Z_{>0}. The only quibble is phrasing: the model states the theorem as requiring non-integer exponents for every iterate; the paper phrases it as µ_i(f)∉Root, but these are equivalent via Proposition 2.1(ii). Overall, the paper provides the substantive proof, while the model gives a correct, brief application of the paper’s main result.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

This work establishes a robust, verifiable criterion ensuring finiteness of return sets to curves for dense orbits under surjective endomorphisms of projective varieties, using cohomological Lyapunov exponents. The proof integrates linear algebra on N1, height growth, and an Albanese reduction, and is adaptable across characteristics. Clarity is good, with small places where phrasing (notably the abstract’s use of “any”) could better match the precise Root condition, and a few navigational remarks could help readers. The results are significant for arithmetic dynamics and complement existing DML literature.