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Equivalence singularity dichotomies for a class of ergodic measures

Published online by Cambridge University Press:  24 October 2008

Marek Kanter
Affiliation:
Sir George Williams Campus, Concordia University, Montreal

Extract

Let µ be a probability measure on the Borel subsets of R. If D is a countable subgroup of R we say that µ is D-ergodic if (1) for any D invariant Borel subset A of R we have µ(A) = 0 or 1 and (2) if µ*δx ≈ µ for all xD (where δx stands for unit mass at x while the equivalence relation ≈ signifies that the two measures have the same null sets.) We say that x is an admissible translate for µ if µ*δx ≈ µ. We say that µ is D-smooth if sx is an admissible translate for µ for all xD and all sR. We say that µ is a smooth ergodic measure if µ is D-ergodic and D-smooth for some countable subgroup D as above. In this paper we show that any two smooth ergodic probability measures µl, µ2 are either equivalent or singular (where the latter means that there exist disjoint Borel sets Al, A2R such that µi(Ai) = 1 and is signified by µ1 ┴ µ2). It is important to note that the countable subgroup D1 associated with µl need not be the same as the subgroup D2 associated with µ2.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1977

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