%0 Journal Article
%T An omega-power of a context-free language which is Borel above Delta^0_omega
%A Jacques Duparc
%A Olivier Finkel
%J Mathematics
%D 2008
%I arXiv
%X 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.
%U http://arxiv.org/abs/0801.1783v1