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Embedding locales and formal topologies into positive topologies

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Abstract

A positive topology is a set equipped with two particular relations between elements and subsets of that set: a convergent cover relation and a positivity relation. A set equipped with a convergent cover relation is a predicative counterpart of a locale, where the given set plays the role of a set of generators, typically a base, and the cover encodes the relations between generators. A positivity relation enriches the structure of a locale; among other things, it is a tool to study some particular subobjects, namely the overt weakly closed sublocales. We relate the category of locales to that of positive topologies and we show that the former is a reflective subcategory of the latter. We then generalize such a result to the (opposite of the) category of suplattices, which we present by means of (not necessarily convergent) cover relations. Finally, we show that the category of positive topologies also generalizes that of formal topologies, that is, overt locales.

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Acknowledgements

We thank our colleagues and friends Maria Emilia Maietti, Samuele Maschio and Tatsuji Kawai for their comments and suggestions.

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Authors and Affiliations

  1. Department of Mathematics, University of Padova, Via Trieste 63, 35121, Padua, Italy

    Francesco Ciraulo & Giovanni Sambin

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  1. Francesco Ciraulo
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  2. Giovanni Sambin
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Correspondence to Francesco Ciraulo.

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Ciraulo, F., Sambin, G. Embedding locales and formal topologies into positive topologies. Arch. Math. Logic 57, 755–768 (2018). https://doi.org/10.1007/s00153-017-0605-0

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  • DOI: https://doi.org/10.1007/s00153-017-0605-0

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