The cut-by-curves conjecture for overconvergent F-isocrystals

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Let XX be a variety, let YY be a boundary or compactification datum, and let CC denote a curve contained in the indicated variety. Write F−Isoc⁡(X)\operatorname{\mathbf{F-Isoc}}(X) and F−Isoc⁡(X,Y)\operatorname{\mathbf{F-Isoc}}(X,Y) for the convergent categories with and without the boundary structure, and F−Isoc⁡†(X)\operatorname{\mathbf{F-Isoc}}^\dagger(X) for the overconvergent category. Cut-by-curves conjecture. An object of F−Isoc⁡(X)\operatorname{\mathbf{F-Isoc}}(X) extends to F−Isoc⁡(X,Y)\operatorname{\mathbf{F-Isoc}}(X,Y) if and only if, for every curve C⊆YC \subseteq Y, its pullback to F−Isoc⁡(C×YX)\operatorname{\mathbf{F-Isoc}}(C \times_Y X) extends to F−Isoc⁡(C×YX,C)\operatorname{\mathbf{F-Isoc}}(C \times_Y X,C). In particular, an object of F−Isoc⁡(X)\operatorname{\mathbf{F-Isoc}}(X) extends to F−Isoc⁡†(X)\operatorname{\mathbf{F-Isoc}}^\dagger(X) if and only if, for every curve C⊆XC \subseteq X, its pullback to F−Isoc⁡(C)\operatorname{\mathbf{F-Isoc}}(C) extends to F−Isoc⁡†(C)\operatorname{\mathbf{F-Isoc}}^\dagger(C). This is known for unit-root objects, while weaker results require the underlying connection to extend to a strict neighborhood.

References

Primary source

Kiran S. Kedlaya, “Notes on isocrystals”, arXiv:1606.01321 (2022).

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