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On extension of Baire submeasures. (English) Zbl 0606.28010
Let T be a locally compact topological space. It is well known that each Baire measure on it can be extended uniquely to a regular Borel measure. In a previous paper of the author [Diss. Math. 112, 35 p. (1974; Zbl 0292.28001)] this result was generalized to submeasures. In the present paper a new proof is presented. It is based on the following observation. If $$\mu$$ is a regular Borel (sub)measure, then to each Borel set A there is a Baire set E such that $$A\Delta E$$ is a $$\mu$$-null set. Thus to extend a Baire submeasure it suffices to define appropriate $$\sigma$$- ideal of ”null”sets. This method is known at least since P. A. Meyer’s ”Probabilités et potentiel” (1966; Zbl 0138.104)]. The definition of submeasure used here does not contain subadditivity, but by the work of L. Drewnowski [Colloq. Math. 38, 243-253 (1978; Zbl 0398.28003)] this is in fact inessential. The proofs are in the same vein as in P. R. Halmos’ ”Measure theory” (1950; Zbl 0040.168)].
Reviewer: B.Aniszczyk

MSC:
 28C15 Set functions and measures on topological spaces (regularity of measures, etc.) 28A12 Contents, measures, outer measures, capacities
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References:
 [1] BERBERIAN S. K.: Measure and Integration. New York-London 1965. · Zbl 0126.08001 [2] BERBERIAN S. K.: On the extension of Borel Measures. Proc. Amer. Math. Soc. 16 1965, 415-418. · Zbl 0145.28101 [3] DOBRAKOV I.: On submeasures I. Dissertationes Math. 112, Warszawa 1974. · Zbl 0292.28001 [4] DOBRAKOV I., FARKOVÁ J.: On submeasures II. Math. Slovaca 30 1980, 65-81. · Zbl 0428.28001 [5] DOBRAKOV I.: A concept of measurability for the Daniell integral. Math. Slovaca 28 1978, 361-378. · Zbl 0414.28009 [6] HALMOS P. R.: Measure Theory. New York 1950. · Zbl 0040.16802
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