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Definability properties and the congruence closure
Authors:Xavier Caicedo
Institution:(1) Departamento de Matemáticas, Universidad Nacional de Colombia, Apartado aéreo 2509, Bogota, Colombia
Abstract:We introduce a natural class of quantifiersTh containing all monadic type quantifiers, all quantifiers for linear orders, quantifiers for isomorphism, Ramsey type quantifiers, and plenty more, showing that no sublogic ofL ohgrohgr (Th) or countably compact regular sublogic ofL infinohgr (Th), properly extendingL ohgrohgr , satisfies the uniform reduction property for quotients. As a consequence, none of these logics satisfies eitherDelta-interpolation or Beth's definability theorem when closed under relativizations. We also show the failure of both properties for any sublogic ofL infinohgr (Th) in which Chang's quantifier or some cardinality quantifierQ agr, with agrgE1, is definable.
Keywords:
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