The Toposic Hom Conjecture

Let KK be an absolutely finitely generated field, meaning that it is finitely generated over its prime field. Let

C=SchKft[UH1]\mathscr{C}=\mathbf{Sch}_{K}^{\operatorname{ft}}[\operatorname{UH}^{-1}]

be the localization of the category of finite type KK-schemes at the universal homeomorphisms, and let X,YOb(C)X,Y\in\operatorname{Ob}(\mathscr{C}). Write Shv(Xeˊt)\operatorname{Shv}(X_{\operatorname{\acute et}}) and Shv(Yeˊt)\operatorname{Shv}(Y_{\operatorname{\acute et}}) for their étale topoi, and let the superscript \bullet denote the class of admissible morphisms specified in the source. The Toposic Hom Conjecture. The natural map

MorC(X,Y)MorShv(Keˊt)(Shv(Xeˊt),Shv(Yeˊt))\operatorname{Mor}_{\mathscr{C}}(X,Y)\longrightarrow \operatorname{Mor}_{\operatorname{Shv}(K_{\operatorname{\acute et}})}^\bullet(\operatorname{Shv}(X_{\operatorname{\acute et}}),\operatorname{Shv}(Y_{\operatorname{\acute et}}))

is a bijection. This is the paper's general étale reconstruction statement; the supplied material does not state whether it is proved in full generality, so its resolution remains to be checked.

Sources & referencesView supporting material

Primary source

Zachary Berens, “Étale Reconstruction for F_p(t)-Schemes”, arXiv:2509.23485 (2025).

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