The Borel complexity of von Neumann equivalence
نویسندگان
چکیده
We prove that for a countable discrete group Γ containing copy of the free Fn, some 2≤n≤∞, as normal subgroup, equivalence relations conjugacy, orbit and von Neumann ergodic a.e. probability measure preserving actions are analytic non-Borel in Polish space Γ-actions. As consequence we obtain isomorphism spaces separably acting factors type II1, II∞ IIIλ, 0≤λ≤1, not Borel when these given Effros structure.
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ژورنال
عنوان ژورنال: Annals of Pure and Applied Logic
سال: 2021
ISSN: ['0168-0072', '1873-2461']
DOI: https://doi.org/10.1016/j.apal.2020.102913