REVIEW
On Vojta's harder implication, height inequalities for admissible pairs, points of bounded degree and Deligne-Mumford stacks
Number Theory · Submitted 28 Sep 2026 · 26 references
Pith's verdict: A genuine conditional-theory paper with an honest lineage, but the hard direction of the equivalence rests on Lemma 3.7's condition (3.2), which is not satisfiable for dim >= 2 as written — the fix is to excise Supp(D*) — and the stack theorems have fixable statement gaps.
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Referee report
The paper
The paper claims
The paper proves that Vojta's bounded-degree inequality with discriminant term, Levin's admissible-pairs inequality, and its truncated form are logically equivalent, and derives a conditional Bombieri-Lang statement for Deligne-Mumford…
The reading
What carries the argument
The engine is the ramified $e$-fold cover $\pi: X' \to X$ of Lemma 3.6, which combines Vojta's Lemmas 3.3 and 3.4: it takes $e$-th roots of functions $f_i$ whose divisors are $A - D_i$, so that all components of $\pi^*D_1$ have multiplicity at least $e$. On this cover, the truncated counting function $n_S^{(1)}(D_1, x)$ dominates $(e-1)n_S^{(1)}(D_1', x')$, and the discriminant transform is governed by condition (3.2), so the two sides of the desired inequality can be matched. The second engine is Lemma 5.1, a Silverman-type bound $d_K(y) \le (2r-2)m_0 h_M(y) + O(1)$ that turns unbounded height into a discriminant bound, which combines with the splitting hypothesis $K_{(Y,D_0)}^{\otimes m} \simeq M^{\otimes n} \otimes N$ with $n > m m_0 (2r-2)$ to produce finiteness via the Northcott property.
Extended reading notes
Core claim
The central claim is stated as Theorem 1.4: Conjecture 1.1 (Vojta's bounded-degree inequality with discriminant term), Conjecture 1.2 (the admissible-pairs inequality for $(D_0,S)$-integral points), and Conjecture 1.3 (its truncated form) are pairwise logically equivalent. The genuinely new step is the harder implication, Conjecture 1.2 implying Conjecture 1.3, which is established by adapting Vojta's ramified-cover approach to the abc conjecture: one pulls back through a cover where all components of $\pi^*D_1$ have multiplicity at least $e$, uses the discriminant-transformation inequality of Lemma 3.7, and matches the truncated counting function on $X$ against the full counting function on $X'$. The paper further proves (Theorems 1.7 and 5.3) that, conditionally on Conjecture 1.1, certain general-type nonsingular Deligne-Mumford stacks with projective coarse moduli space have a non-Zariski-dense set of $(D_0,S)$-integral points of bounded degree, a form of the Bombieri-Lang conjecture for stacks.
Load-bearing premise
The load-bearing premise is condition (3.2): after enlarging the finite set of places $S$, the discriminant gap $d_{K,S}(x') - d_{K,S}(x)$ between a bounded-degree point and its lift to the ramified cover must be bounded by $(e-1)n_S^{(1)}(D', x')$, a condition the paper justifies in a single sentence by citing Hermite's discriminant theorem without supplying the argument. If that inequality cannot always be met, the equivalence theorem collapses at its hard direction.
Editorial extensions
If this is right
- Conjectures 1.1, 1.2 and 1.3 stand or fall together: a proof of any one of the three yields the other two, in the spirit in which the abc Conjecture and Vojta's inequality were meant to be interlocked.
- If Conjecture 1.1 holds, then for nonsingular Deligne-Mumford stacks with projective coarse moduli space whose log canonical bundle is big and splits as $K_{(X,D_0)}^{\otimes m} \simeq M^{\otimes n} \otimes N$ with $n > m m_0(2r-2)$, the set of $(D_0,S)$-integral points of degree at most $d$ is not Zariski dense.
- Working on the finite cover of Theorem 1.5 avoids the stack-theoretic discriminant term and the absence of a Northcott property for big line bundles that arise when formulating height inequalities directly on the underlying stack.
Reading between the lines
- Condition (3.2) is the point most worth probing: if the Hermite-discriminant justification in Remark 3.8 cannot be turned into an unconditional argument for the specific covers of Lemma 3.6, then Theorem 1.4 still gives the equivalence of Conjectures 1.1 and 1.2, but the truncated-form equivalence in Conjecture 1.3 would hang unresolved.
- The splitting hypothesis $n > m m_0(2r-2)$ confines the Bombieri-Lang application to log pairs whose log canonical bundle is very nearly a power of an ample line bundle; the genuinely general-type pairs, where the log canonical bundle is big but not nearly ample, lie outside the scope, and extending the argument there is a natural next step.
- The Silverman-type bound of Lemma 5.1 is explicitly non-optimal (Remark 5.2), so the constant $(2r-2)$ that forces the strong splitting hypothesis might be improvable; tightening it would directly widen the class of stacks covered by Theorem 1.7.
Original abstract
We expand on the concept of \emph{admissible pairs} from \cite{Levin:GCD} and explore its relation with the main Diophantine arithmetic inequalities, with discriminant term and for points of bounded degree, that have been predicted by Vojta \cite{Vojta:1998}. In this context, among other new results, we prove a \emph{harder implication} which is in the spirit of Vojta's approach to the abc Conjecture (from \cite{Vojta:1998}). As our main result, and application of our viewpoint here, we deduce for the case of certain general type nonsingular Deligne-Mumford stacks, with projective course moduli space, a form of the Bombieri-Lang Conjecture for $(D_0,S)$-integral points of bounded degree. A key input for this is a slicing theorem, for Deligne-Mumford stacks, that was obtained by Abramovich and V\'{a}rilly-Alvarado, \cite{Abramovich:VarillyAlvarado:Pera:2017}, and building on earlier work of Kresch and Vistoli \cite{Kresch:Vistoli:2004}. Another important ingredient is an inequality of Silverman, from \cite{Silverman:1984}, which bounds the discriminant of points in projective space in terms of their heights. As an illustration of our results, we discuss them within the context of the interesting work of Abramovich and Harris \cite{Abramovich:Harris:1991} and others.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We expand on the concept of \emph{admissible pairs} from \cite{Levin:GCD} and explore its relation with the main Diophantine arithmetic inequalities, with discriminant term and for points of bounded degree, that have been predicted by Vojta \cite{Vojta:1998}. In this context, among other new results, we prove a \emph{harder implication} which is in the spirit of Vojta's approach to the abc Conjecture (from \cite{Vojta:1998}). As our main result, and application of our viewpoint here, we deduce for the case of certain general type nonsingular Deligne-Mumford stacks, with projective course moduli space, a form of the Bombieri-Lang Conjecture for $(D_0,S)$-integral points of bounded degree. A key input for this is a slicing theorem, for Deligne-Mumford stacks, that was obtained by Abramovich and V\'{a}rilly-Alvarado, \cite{Abramovich:VarillyAlvarado:Pera:2017}, and building on earlier work of Kresch and Vistoli \cite{Kresch:Vistoli:2004}. Another important ingredient is an inequality of Silverman, from \cite{Silverman:1984}, which bounds the discriminant of points in projective space in terms of their heights. As an illustration of our results, we discuss them within the context of the interesting work of Abramovich and Harris \cite{Abramovich:Harris:1991} and others.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We expand on the concept of \emph{admissible pairs} from \cite{Levin:GCD} and explore its relation with the main Diophantine arithmetic inequalities, with discriminant term and for points of bounded degree, that have been predicted by Vojta \cite{Vojta:1998}. | contribution 0.79 | 0.79 | 0.05 | asserted 0.91 |
| s1 | In this context, among other new results, we prove a \emph{harder implication} which is in the spirit of Vojta's approach to the abc Conjecture (from \cite{Vojta:1998}). | result 0.69 | 0.95 | 0.09 | asserted 1.00 |
| s2 | As our main result, and application of our viewpoint here, we deduce for the case of certain general type nonsingular Deligne-Mumford stacks, with projective course moduli space, a form of the Bombieri-Lang Conjecture for $(D_0,S)$-integral points of bounded degree. | result 0.99 | 0.95 | 0.96 | asserted 1.00 |
| s3 | A key input for this is a slicing theorem, for Deligne-Mumford stacks, that was obtained by Abramovich and V\'{a}rilly-Alvarado, \cite{Abramovich:VarillyAlvarado:Pera:2017}, and building on earlier work of Kresch and Vistoli \cite{Kresch:Vistoli:2004}. | method 0.77 | 0.04 | 0.02 | asserted 1.00 |
| s4 | Another important ingredient is an inequality of Silverman, from \cite{Silverman:1984}, which bounds the discriminant of points in projective space in terms of their heights. | method 0.62 | 0.04 | 0.02 | asserted 1.00 |
| s5 | As an illustration of our results, we discuss them within the context of the interesting work of Abramovich and Harris \cite{Abramovich:Harris:1991} and others. | contribution 0.48 | 0.50 | 0.02 | asserted 0.62 |
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