On the first-order theories of quaternions and octonions

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Auteur principal: Savi, Enrico
Format: Preprint
Publié: 2024
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author Savi, Enrico
author_facet Savi, Enrico
contents Let $L$ be the language of rings. We provide an axiomatization of the $L$-theories of quaternions and octonions and characterize their models: they coincide, up to isomorphism, with quaternion and octonion algebras over a real closed field, respectively. We bi-interpret these theories in terms of real closed fields and we prove they are complete, model complete and they do not have quantifier elimination. Then, we focus on the class of ordered polynomials. Over $\mathbb{H}$ and $\mathbb{O}$ these polynomials are of special interest in hypercomplex analysis since they are slice regular. We deduce some fundamental properties of their zero loci from model completeness and we introduce the notions of algebraic sets and Zariski topology. Finally, we prove the failure of quantifier elimination for the fragment of ordered formulas and we completely characterize the family of algebraic sets.
format Preprint
id arxiv_https___arxiv_org_abs_2404_04976
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle On the first-order theories of quaternions and octonions
Savi, Enrico
Algebraic Geometry
Logic
Rings and Algebras
03C60 (Primary), 03C10, 03C64, 16K20, 17A35, 30G35 (Secondary)
Let $L$ be the language of rings. We provide an axiomatization of the $L$-theories of quaternions and octonions and characterize their models: they coincide, up to isomorphism, with quaternion and octonion algebras over a real closed field, respectively. We bi-interpret these theories in terms of real closed fields and we prove they are complete, model complete and they do not have quantifier elimination. Then, we focus on the class of ordered polynomials. Over $\mathbb{H}$ and $\mathbb{O}$ these polynomials are of special interest in hypercomplex analysis since they are slice regular. We deduce some fundamental properties of their zero loci from model completeness and we introduce the notions of algebraic sets and Zariski topology. Finally, we prove the failure of quantifier elimination for the fragment of ordered formulas and we completely characterize the family of algebraic sets.
title On the first-order theories of quaternions and octonions
topic Algebraic Geometry
Logic
Rings and Algebras
03C60 (Primary), 03C10, 03C64, 16K20, 17A35, 30G35 (Secondary)
url https://arxiv.org/abs/2404.04976