Every Borel function is monotone Borel
نویسندگان
چکیده
منابع مشابه
On monotone presentations of Borel sets
If A is a Σξ set and An (n < ω) are Borel sets then we call {An : n < ω} a presentation of A if A = S n<ω An and An (n < ω) have lower Borel class than A has. We show that for 2 ≤ ξ < ω1 it is not possible to assign a presentation to Σξ sets in a monotone way, i.e., it is not possible to define functions fn : Σ 0 ξ → Πξ (n < ω) such that for every A ∈ Σξ we have A = S n<ω fn(A) and A,A ′ ∈ Σξ, ...
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ژورنال
عنوان ژورنال: Annals of Pure and Applied Logic
سال: 1991
ISSN: 0168-0072
DOI: 10.1016/0168-0072(91)90010-j