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Borel Ranks and Wadge Degrees of Context Free Omega Languages
[article]

2007
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arXiv
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pre-print

We show that, from a topological point of view, considering the Borel and the Wadge hierarchies, 1-counter B\"uchi automata have the same accepting power than Turing machines equipped with a B\"uchi acceptance condition. In particular, for every non null recursive ordinal alpha, there exist some Sigma^0_alpha-complete and some Pi^0_alpha-complete omega context free languages accepted by 1-counter B\"uchi automata, and the supremum of the set of Borel ranks of context free omega languages is the

arXiv:0712.1359v1
fatcat:neek5lsw3zctbfsblzevl3vbvq