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SET IDEALS WITH ISOMORPHIC SYMMETRY GROUPS
Published online by Cambridge University Press: 18 January 2002
Abstract
A criterion of isomorphism for symmetry groups of set ideals is provided in terms of ideal quotients and cardinal invariants. Furthermore, set ideals with complete symmetry group are characterized. They form a wide class, comprising, for example, all uniform dense ideals and the ideals of ‘thin’ sets in separable metric spaces. If the symmetry group of a set ideal is not complete, then its outer automorphism group is shown to be cyclic of order 2.
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- © The London Mathematical Society 2002
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