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Spatiality of countably presentable locales (proved with the Baire category theorem)

Published online by Cambridge University Press:  10 November 2014

REINHOLD HECKMANN
REINHOLD HECKMANN*
Affiliation:
AbsInt Angewandte Informatik GmbH, Science Park 1, D-66123 Saarbrücken, Germany Email: [email protected]
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Abstract

The first part of the paper presents a generalization of the well-known Baire category theorem. The generalization consists in replacing the dense open sets of the original formulation by dense UCO sets, where UCO means union of closed and open. This topological theorem is exactly what is needed to prove in the second part of the paper the locale-theoretic result that locales whose frame of opens has a countable presentation (countably many generators and countably many relations) are spatial. This spatiality theorem does not require choice.

Type
Paper
Information
Mathematical Structures in Computer Science , Volume 25 , Special Issue 7: Computing with Infinite Data: Topological and Logical Foundations Part 1 , October 2015 , pp. 1607 - 1625
Copyright
Copyright © Cambridge University Press 2014 

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