Wadge hierarchy of omega context-free languages

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Abstract

The main result of this paper is that the length of the Wadge hierarchy of omega context-free languages is greater than the Cantor ordinal ε0, and the same result holds for the conciliating Wadge hierarchy, defined by Duparc (J. Symbolic Logic, to appear), of infinitary context-free languages, studied by Beauquier (Ph.D. Thesis, Université Paris 7, 1984). In the course of our proof, we get results on the Wadge hierarchy of iterated counter ω-languages, which we define as an extension of classical (finitary) iterated counter languages to ω-languages.

Keywords

Omega context-free languages
Topological properties
Wadge hierarchy
Conciliating Wadge hierarchy
Infinitary context-free languages
Iterated counter ω-languages

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