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| Format: | Preprint |
| Veröffentlicht: |
2024
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| Online-Zugang: | https://arxiv.org/abs/2409.11231 |
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| _version_ | 1866915762684297216 |
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| author | Kanalas, Kristóf |
| author_facet | Kanalas, Kristóf |
| contents | We study positively closed and strongly positively closed topos-valued models of coherent theories. Positively closed is a global notion (it is defined in terms of all possible outgoing homomorphisms), while strongly positively closed is a local notion (it only concerns the definable sets inside the model). For $\mathbf{Set}$-valued models of coherent theories they coincide.
We prove that if $\mathcal{E}=Sh(B,τ_{coh})$ for a complete Boolean algebra, then positively closed but not strongly positively closed $\mathcal{E}$-valued models of coherent theories exist, yet, there is an alternative local property which characterizes positively closed $\mathcal{E}$-valued models.
A large part of our discussion is given in the context of infinite quantifier geometric logic, dealing with the fragment $L^g_{κκ}$ where $κ$ is weakly compact. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2409_11231 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Positively closed $Sh(B)$-valued models Kanalas, Kristóf Category Theory Logic We study positively closed and strongly positively closed topos-valued models of coherent theories. Positively closed is a global notion (it is defined in terms of all possible outgoing homomorphisms), while strongly positively closed is a local notion (it only concerns the definable sets inside the model). For $\mathbf{Set}$-valued models of coherent theories they coincide. We prove that if $\mathcal{E}=Sh(B,τ_{coh})$ for a complete Boolean algebra, then positively closed but not strongly positively closed $\mathcal{E}$-valued models of coherent theories exist, yet, there is an alternative local property which characterizes positively closed $\mathcal{E}$-valued models. A large part of our discussion is given in the context of infinite quantifier geometric logic, dealing with the fragment $L^g_{κκ}$ where $κ$ is weakly compact. |
| title | Positively closed $Sh(B)$-valued models |
| topic | Category Theory Logic |
| url | https://arxiv.org/abs/2409.11231 |