Locally finite ω-languages and effective analytic sets have the same topological complexity
نویسنده
چکیده
Local sentences and the formal languages they define were introduced by Ressayre in [Res88]. We prove that locally finite ω-languages and effective analytic sets have the same topological complexity: the Borel and Wadge hierarchies of the class of locally finite ω-languages are equal to the Borel and Wadge hierarchies of the class of effective analytic sets. In particular, for each non-null recursive ordinal α < ω 1 there exist some Σ 0 α-complete and some Π 0 αcomplete locally finite ω-languages, and the supremum of the set of Borel ranks of locally finite ω-languages is the ordinal γ 2 , which is strictly greater than the first non-recursive ordinal ω 1 . This gives an answer to the question of the topological complexity of locally finite ωlanguages, which was asked by Simonnet [Sim92] and also by Duparc, Finkel, and Ressayre in [DFR01]. Moreover we show that the topological complexity of a locally finite ω-language defined by a local sentence φ may depend on the models of the Zermelo-Fraenkel axiomatic system ZFC. Using similar constructions as in the proof of the above results we also show that the equivalence, the inclusion, and the universality problems for locally finite ω-languages are Π2-complete, hence highly undecidable.
منابع مشابه
Topological complexity of locally finite omega -languages
Locally finite omega languages were introduced by Ressayre in [Formal Languages defined by the Underlying Structure of their Words, Journal of Symbolic Logic, 53, number 4, December 1988, p. 1009-1026]. These languages are defined by local sentences and extend ω-languages accepted by Büchi automata or defined by monadic second order sentences. We investigate their topological complexity. All lo...
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ورودعنوان ژورنال:
- Math. Log. Q.
دوره 62 شماره
صفحات -
تاریخ انتشار 2016