Computability in Europe 2008
Logic and Theory of Algorithms 

Regular Talk:

Author(s):  Jacques Duparc and Alessandro Facchini 
Slot:  Tue, 12:2012:40, Room 22 (col. 4) 
The height of the Wadge Hierarchy for the Alternation Free Fragment of $\mu$calculus is known to be at least $\epsilon_{0}$. It was conjectured that the height is exactly $\epsilon_{0}$. We make a first step towards the proof of this conjecture by showing that there is no $\Delta^\mu_{2}$ definable set in between the levels $\omega^\omega$ and $\omega_{1}$ of the Wadge Hierarchy of Borel Sets.
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