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arXiv · 2411.18846

The Unipotent Chabauty-Kim-Kantor Method for Relative Completions

David Corwin·Sa'ar Zehavi
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Abstract

We develop a new $p$-adic analytic method for studying integral points on hyperbolic curves, building on Kantor's relative-completion approach to unifying the Chabauty-Kim and Lawrence-Venkatesh methods. Its central mechanism converts dimension inequalities between algebraic global and local Galois cohomology stacks into nonzero rigid-analytic functions vanishing on the integral points within a residue disk. Assuming the relevant Bloch-Kato dimension formulas, we verify these inequalities for curves of genus at least $2$, as well as for certain modular curves, and thereby obtain a new conditional proof of the theorems of Faltings and Siegel. Our method produces genuinely new functions, different from those produced by Chabauty-Kim, pointing to an improved effective approach. Our key technical contributions include the following. We prove that Kantor's $p$-adic period map is analytic and algebraically Zariski dense in the relevant period domain. We also bypass the conjectural representability of Kantor's Selmer stacks by decomposing the integral-point locus into finitely many Kummer strata. On each stratum, the relative Kummer map factors through a neutral-fibre Selmer stack, which we prove is an algebraic Artin stack of finite type. We also develop a theory of finite-type motivic quotients of the relative completion: these quotients are cofinal among all finite-type quotients and recover the relative completion as their inverse limit. For Kodaira-Parshin families over curves of genus at least $2$, we construct a canonical adjoint-supported tower with fixed finite-dimensional abelianization and controlled graded pieces. At sufficiently deep levels, the Bloch-Kato formulas imply the required dimension inequality and produce genuinely relative rigid-analytic functions that do not arise from the ordinary unipotent completion.

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BibTeXRIS

David Corwin, Sa'ar Zehavi. 2024-11-28. The Unipotent Chabauty-Kim-Kantor Method for Relative Completions. https://arxiv.org/abs/2411.18846

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