A 2-Categorical Bridge Between Henkin Constructions and Lawvere's Fixed-Point Theorem: Unifying Completeness and Compactness

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1. Verfasser: Reizi, Barreto Joaquim
Format: Preprint
Veröffentlicht: 2025
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author Reizi, Barreto Joaquim
author_facet Reizi, Barreto Joaquim
contents We present a unified categorical framework that connects the syntactic Henkin construction for the first-order Completeness Theorem with Lawvere's Fixed-Point Theorem. Concretely, we define two canonical functors from the category of first-order theories to the category of their models, and then introduce a canonical natural transformation that links the Henkin-based term models to semantically constructed models arising from compactness or saturation arguments. We prove that every component of this natural transformation is an isomorphism, thereby establishing a strong equivalence between the syntactic and semantic perspectives. Furthermore, we show that this transformation is 2-categorically rigid: any other natural transformation in the same setting is uniquely isomorphic to it. Our framework highlights the shared diagonalization principle underlying both Henkin's and Lawvere's methods and demonstrates concrete applications in automated theorem proving, formal verification, and the design of advanced type-theoretic systems.
format Preprint
id arxiv_https___arxiv_org_abs_2504_03797
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A 2-Categorical Bridge Between Henkin Constructions and Lawvere's Fixed-Point Theorem: Unifying Completeness and Compactness
Reizi, Barreto Joaquim
General Mathematics
We present a unified categorical framework that connects the syntactic Henkin construction for the first-order Completeness Theorem with Lawvere's Fixed-Point Theorem. Concretely, we define two canonical functors from the category of first-order theories to the category of their models, and then introduce a canonical natural transformation that links the Henkin-based term models to semantically constructed models arising from compactness or saturation arguments. We prove that every component of this natural transformation is an isomorphism, thereby establishing a strong equivalence between the syntactic and semantic perspectives. Furthermore, we show that this transformation is 2-categorically rigid: any other natural transformation in the same setting is uniquely isomorphic to it. Our framework highlights the shared diagonalization principle underlying both Henkin's and Lawvere's methods and demonstrates concrete applications in automated theorem proving, formal verification, and the design of advanced type-theoretic systems.
title A 2-Categorical Bridge Between Henkin Constructions and Lawvere's Fixed-Point Theorem: Unifying Completeness and Compactness
topic General Mathematics
url https://arxiv.org/abs/2504.03797