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On the theories classified by an étendue (2507.04526v1)
Published 6 Jul 2025 in math.LO and math.CT
Abstract: We give a model-theoretic characterisation of the geometric theories classified by \'etendues -- the `locally localic' topoi. They are the theories where each model is determined, syntactically and semantically, by any witness of a fixed collection of formulae.