Towards Cohomology of Real Closed Spaces

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Auteur principal: Clarke-James, Tafari
Format: Preprint
Publié: 2024
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author Clarke-James, Tafari
author_facet Clarke-James, Tafari
contents It was shown by Claus Scheiderer prior to 1994 that real closed spaces have étale cohomology. Following Scheiderer, study of real closed spaces fell out of fashion and o-minimal geometry became the focus for those at the intersection of model theory and geometry. I decided to breathe new life into the theory of real closed rings and spaces, as studied by Schwartz in 1989. In Section 1, I build the fundamentals of the theory using as little machinery as possible, and presented them as clearly as I could. Hidden gems include a full proof that real closed rings are closed under limits and colimits. In Section 2, I give an introduction to the category of real closed spaces in the first half. In the second half, I construct an equivalence of topoi between Scheiderer's sheaves on the real étale site, and sheaves on a real étale site $\rce/X$ of my creation. Since $\text{Sh}(\rce/X)$ can be defined without the use of $G$-topoi, the equivalence of topoi renders Scheiderer's theory computable. I end with a discussion of how one might use motivic cohomology to better understand recent results of Annette Huber in \cite{no_deRham_huber}.
format Preprint
id arxiv_https___arxiv_org_abs_2410_19929
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Towards Cohomology of Real Closed Spaces
Clarke-James, Tafari
Algebraic Geometry
Algebraic Topology
Rings and Algebras
14
It was shown by Claus Scheiderer prior to 1994 that real closed spaces have étale cohomology. Following Scheiderer, study of real closed spaces fell out of fashion and o-minimal geometry became the focus for those at the intersection of model theory and geometry. I decided to breathe new life into the theory of real closed rings and spaces, as studied by Schwartz in 1989. In Section 1, I build the fundamentals of the theory using as little machinery as possible, and presented them as clearly as I could. Hidden gems include a full proof that real closed rings are closed under limits and colimits. In Section 2, I give an introduction to the category of real closed spaces in the first half. In the second half, I construct an equivalence of topoi between Scheiderer's sheaves on the real étale site, and sheaves on a real étale site $\rce/X$ of my creation. Since $\text{Sh}(\rce/X)$ can be defined without the use of $G$-topoi, the equivalence of topoi renders Scheiderer's theory computable. I end with a discussion of how one might use motivic cohomology to better understand recent results of Annette Huber in \cite{no_deRham_huber}.
title Towards Cohomology of Real Closed Spaces
topic Algebraic Geometry
Algebraic Topology
Rings and Algebras
14
url https://arxiv.org/abs/2410.19929