Countable ordinals and the analytical hierarchy, II
نویسندگان
چکیده
منابع مشابه
Countable Ordinals and the Analytical Hierarchy, I
Proof. For notational simplicity let us take n = 1 as a typical case. Thus let A C WO be ΣJ and assume sup {|a |: a E A} < Nj. Let B Qω be Π2 and /: ω ->ω recursive such that f[B] = A. Consider then the following game: Player I plays β, player II plays γ and II wins iff γ E WO&(β E B -> \f(β)| g | γ | ) . Clearly player II has a winning strategy in this game. But his payoff set is Σ\9 so by a r...
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ژورنال
عنوان ژورنال: Annals of Mathematical Logic
سال: 1978
ISSN: 0003-4843
DOI: 10.1016/0003-4843(78)90010-4