Abstract
We give a self-contained proof of the following result: Finitely additive probability measures (also known as “states”) of the free boolean algebra \({\mathsf F}_\omega \) over the free generating set \(\{X_1,X_2,\ldots \}\) having the invariance property under finite permutations of the \(X_i\), coincide with states lying in the closure of the set of convex combinations of product states of \({\mathsf F}_\omega \) in the vector space \(\mathbb R^{{\mathsf F}_\omega }\) equipped with the product topology. De Finetti’s celebrated exchangeability theorem can be easily recovered from our proof.
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Presented by K. A. Kearnes.
To Bruno de Finetti, in memoriam.
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Mundici, D. Permutation invariant boolean states. Algebra Univers. 85, 27 (2024). https://doi.org/10.1007/s00012-024-00859-3
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DOI: https://doi.org/10.1007/s00012-024-00859-3
Keywords
- Free boolean algebra
- Finitely additive measure
- Product state
- Exchangeable state
- de Finetti exchangeability theorem
- de Finetti representation theorem