Abstract
Let (Ω,ℬ,P) be a probability space, \(\mathcal{A}\subset\mathcal{B}\) a sub-σ-field, and μ a regular conditional distribution for P given \(\mathcal{A}\) . For various, classically interesting, choices of \(\mathcal{A}\) (including tail and symmetric), we prove the following 0–1 law: There is a set \(A_{0}\in\mathcal{A}\) such that P(A 0)=1 and μ(ω)(A)∈{0,1} for all \(A\in\mathcal{A}\) and ω∈A 0. If ℬ is countably generated (and certain regular conditional distributions exist), the result applies whatever P is.
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Berti, P., Rigo, P. A Conditional 0–1 Law for the Symmetric σ-field. J Theor Probab 21, 517–526 (2008). https://doi.org/10.1007/s10959-008-0174-6
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DOI: https://doi.org/10.1007/s10959-008-0174-6