2 research outputs found
On the Length of the Wadge Hierarchy of Omega Context Free Languages
We prove in this paper that the length of the Wadge hierarchy of omega
context free languages is greater than the Cantor ordinal epsilon_omega, which
is the omega-th fixed point of the ordinal exponentiation of base omega. The
same result holds for the conciliating Wadge hierarchy, defined by J. Duparc,
of infinitary context free languages, studied by D. Beauquier. We show also
that there exist some omega context free languages which are
Sigma^0_omega-complete Borel sets, improving previous results on omega context
free languages and the Borel hierarchy