On the Length of the Wadge Hierarchy of Omega Context Free Languages

Olivier Finkel (1)

1 ELM - Équipe de Logique Mathématique

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.

Domaines: Logique en informatique [cs.LO]; Complexité [cs.CC]; Informatique et théorie des jeux [cs.GT]; Logique [math.LO]

Olivier Finkel. On the Length of the Wadge Hierarchy of Omega Context Free Languages. Journal of Automata Languages and Combinatorics, 2005, 10 (4), pp.439-464. ⟨hal-00122154v2⟩