On a construct of closure spaces (Q1373391)
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scientific article; zbMATH DE number 1089764
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | On a construct of closure spaces |
scientific article; zbMATH DE number 1089764 |
Statements
On a construct of closure spaces (English)
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17 March 1998
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Let \({\mathcal C}lo\) be the construct of closure spaces and continuous mappings. Let \({\mathcal C}lo_T\) be the full subconstruct of \({\mathcal C}lo\) formed by all spaces \((X,u)\in {\mathcal C}lo\) such that for every \(A\subseteq X\) and for every \(x\in uA\) there exists a sequence \(\{x_i\mid i\in\omega \}\) indexed by an ordinal \(\omega\) such that \(x_i\in u\{x_j\mid j<i\}\) for all \(i\in\omega\) and \(x\in u\{x_i\mid i\in\omega \}\). Let \({\mathcal C}lo_S\) be the full subconstruct of \({\mathcal C}lo\) formed by all spaces \((X,u)\in{\mathcal C}lo\) such that \(u(uA)=uA=\bigcup_{x\in A}u\{x\}\) for all \(A\subseteq X\). A space from \({\mathcal C}lo_S\) is called a finitely generated topological space (or a quasi-discrete topological space, or an \(S\)-space, respectively). Let \(\mathcal K\) be a construct with finite products and let \(\mathcal L\) be a full isomorphic closed subconstruct of \(\mathcal K\). We say that \(\mathcal K\) is an exponential superconstruct of \(\mathcal L\) provided that for any two objects \(G\in \mathcal L\) and \(H\in \mathcal K\) there exists a power object \(G^H\in \mathcal K\) such that \(G^H\in \mathcal L\) and a pair \((G^H,e)\), where \(e\) is an evaluation map, which is a co-universal map for \(G\) with respect to the functor \(H\times -:\mathcal K\to\mathcal K\). Then, \({\mathcal C}lo_T\) is an exponential superconstruct of \({\mathcal C}lo_S\). This fact generalizes that \({\mathcal C}lo_S\) is cartesian closed.
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closure space
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exponential object
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full subconstruct
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