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arXiv · 0808.1519

De Morgan classifying toposes

Olivia Caramello
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Abstract

We present a general method for deciding whether a Grothendieck topos satisfies De Morgan's law (resp. the law of excluded middle) or not; applications to the theory of classifying toposes follow. Specifically, we obtain a syntactic characterization of the class of geometric theories whose classifying toposes satisfy De Morgan's law (resp. are Boolean), as well as model-theoretic criteria for theories whose classifying toposes arise as localizations of a given presheaf topos.

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Olivia Caramello. 2008-08-11. De Morgan classifying toposes. https://arxiv.org/abs/0808.1519

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