2 research outputs found
An omega-power of a context-free language which is Borel above Delta^0_omega
We use erasers-like basic operations on words to construct a set that is both
Borel and above Delta^0_omega, built as a set V^\omega where V is a language of
finite words accepted by a pushdown automaton. In particular, this gives a
first example of an omega-power of a context free language which is a Borel set
of infinite rank.Comment: To appear in the Proceedings of the International Conference
Foundations of the Formal Sciences V : Infinite Games, November 26th to 29th,
2004, Bonn, Germany, Stefan Bold, Benedikt L\"owe, Thoralf R\"asch, Johan van
Benthem (eds.), College Publications at King's College (Studies in Logic),
200
An omega-power of a context-free language which is Borel above Delta^0_omega
To appear in the Proceedings of the International Conference Foundations of the Formal Sciences V : Infinite Games, November 26th to 29th, 2004, Bonn, Germany, Stefan Bold, Benedikt Löwe, Thoralf Räsch, Johan van Benthem (eds.), College Publications at King's College (Studies in Logic), 2007.International audienceWe use erasers-like basic operations on words to construct a set that is both Borel and above Delta^0_omega, built as a set V^\omega where V is a language of finite words accepted by a pushdown automaton. In particular, this gives a first example of an omega-power of a context free language which is a Borel set of infinite rank