p-Curvature and Non-Abelian Cohomology

Fuente: arXiv
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Hauptverfasser: Lam, Yeuk Hay Joshua, Litt, Daniel
Format: Preprint
Veröffentlicht: 2026
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author Lam, Yeuk Hay Joshua
Litt, Daniel
author_facet Lam, Yeuk Hay Joshua
Litt, Daniel
contents Let $X\to S$ be a smooth projective morphism. Katz proved the Grothendieck-Katz $p$-curvature conjecture for the Gauss-Manin connection on the $i$-th cohomology of $X/S$: if its $p$-curvature vanishes mod $p$ for infinitely many $p$, then the action of $π_1(S,s)$ on $H^i(X_s, \mathbb{Z})$ factors through a finite group. We prove a non-abelian analogue of this statement: if the $p$-curvature of the isomonodromy foliation on the moduli of flat bundles of rank $r$ on $X/S$ vanishes mod $p$ for infinitely many $p$, then the action of $π_1(S,s)$ on the rank $r$ integral characters of $π_1(X_s)$ factors through a finite group. We deduce many new cases of the Bost/Ekedahl--Shepherd-Barron--Taylor conjecture. The proofs rely on a non-abelian version of Katz's formula, and a non-abelian version of the Hodge index theorem.
format Preprint
id arxiv_https___arxiv_org_abs_2601_07933
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle p-Curvature and Non-Abelian Cohomology
Lam, Yeuk Hay Joshua
Litt, Daniel
Algebraic Geometry
Number Theory
Let $X\to S$ be a smooth projective morphism. Katz proved the Grothendieck-Katz $p$-curvature conjecture for the Gauss-Manin connection on the $i$-th cohomology of $X/S$: if its $p$-curvature vanishes mod $p$ for infinitely many $p$, then the action of $π_1(S,s)$ on $H^i(X_s, \mathbb{Z})$ factors through a finite group. We prove a non-abelian analogue of this statement: if the $p$-curvature of the isomonodromy foliation on the moduli of flat bundles of rank $r$ on $X/S$ vanishes mod $p$ for infinitely many $p$, then the action of $π_1(S,s)$ on the rank $r$ integral characters of $π_1(X_s)$ factors through a finite group. We deduce many new cases of the Bost/Ekedahl--Shepherd-Barron--Taylor conjecture. The proofs rely on a non-abelian version of Katz's formula, and a non-abelian version of the Hodge index theorem.
title p-Curvature and Non-Abelian Cohomology
topic Algebraic Geometry
Number Theory
url https://arxiv.org/abs/2601.07933