Centralized PC systems of pushdown automata versus multi-head pushdown automata

Authors:
Friedrich Otto
Affiliations:
Fachbereich Elektrotechnik/Informatik, Universität Kassel, Kassel, Germany
Venue:
DCFS'12 Proceedings of the 14th international conference on Descriptional Complexity of Formal Systems
Year:
2012

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Abstract

In returning mode centralized PC systems of pushdown automata of degree n can simulate n-head pushdown automata (Csuhaj-Varjú et. al. 2000). At DCFS 2009, Balan claimed that also the converse holds. Here we show that Balan's proof of this claim is not correct. Accordingly it is still open whether n-head pushdown automata and centralized PC systems of pushdown automata of degree n working in returning mode accept the same class of languages.