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Proceedings of the American Mathematical Society

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Extensions of isometrically invariant measures on Euclidean spaces

Author: Piotr Zakrzewski
Journal: Proc. Amer. Math. Soc. 110 (1990), 325-331
MSC: Primary 28C10; Secondary 03E05
MathSciNet review: 1021216
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Abstract: We consider countably additive, nonnegative, extended real-valued measures that vanish on singletons.

Given a group $ G$ of isometries of $ {{\mathbf{R}}^n}$ and a $ G$-invariant $ \sigma $-finite measure on $ {{\mathbf{R}}^n}$ we study the problem of determining whether it has a proper $ G$-invariant extension. We prove that it does, provided that the set of all points with uncountable $ G$-orbits is not of measure zero. We also characterize those groups $ G$ for which every $ G$-invariant $ \sigma $-finite measure on $ {{\mathbf{R}}^n}$ has a proper $ G$-invariant extension.

References [Enhancements On Off] (What's this?)

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Keywords: Invariant $ \sigma $-finite measure, isometries of $ {{\mathbf{R}}^n}$, real-valued measurable cardinal
Article copyright: © Copyright 1990 American Mathematical Society

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