Completion of motivic sheaves

Fuente: arXiv
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Main Author: Cisinski, Denis-Charles
Format: Preprint
Published: 2025
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author Cisinski, Denis-Charles
author_facet Cisinski, Denis-Charles
contents We study the process of $\ell$-adic completion of motivic sheaves. We observe that, in equal characteristic, when restricted to constructible objets, it is compatible with the six operations. This implies that one can reconstruct $\ell$-adic sheaves of geometric origin over a scheme of finite type over a field from $\ell$-adic cohomology of smooth schemes. In the case of finite fields, this includes perverse $\ell$-adic sheaves of geometric orgin. However, the analogous behaviour fails systematically in mixed characteristic: the reason is that it would imply strong independence of $\ell$ results that can be proven to be too optimistic.
format Preprint
id arxiv_https___arxiv_org_abs_2503_24033
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Completion of motivic sheaves
Cisinski, Denis-Charles
Algebraic Geometry
K-Theory and Homology
Number Theory
We study the process of $\ell$-adic completion of motivic sheaves. We observe that, in equal characteristic, when restricted to constructible objets, it is compatible with the six operations. This implies that one can reconstruct $\ell$-adic sheaves of geometric origin over a scheme of finite type over a field from $\ell$-adic cohomology of smooth schemes. In the case of finite fields, this includes perverse $\ell$-adic sheaves of geometric orgin. However, the analogous behaviour fails systematically in mixed characteristic: the reason is that it would imply strong independence of $\ell$ results that can be proven to be too optimistic.
title Completion of motivic sheaves
topic Algebraic Geometry
K-Theory and Homology
Number Theory
url https://arxiv.org/abs/2503.24033