Subset Synchronization of Transitive Automata

Vojtěch Vorel
(Charles University in Prague)

We consider the following generalized notion of synchronization: A word is called a reset word of a subset of states of a deterministic finite automaton if it maps all states of the set to a unique state. It is known that the minimum length of such words is superpolynomial in worst cases, namely in a series of substantially nontransitive automata. We present a series of transitive binary automata with a strongly exponential minimum length. This also constitutes a progress in the research of composition sequences initiated by Arto Salomaa, because reset words of subsets are just a special case of composition sequences. Deciding about the existence of a reset word for given automaton and subset is known to be a PSPACE-complete problem, we prove that this holds even if we restrict the problem to transitive binary automata.

In Zoltán Ésik and Zoltán Fülöp: Proceedings 14th International Conference on Automata and Formal Languages (AFL 2014), Szeged, Hungary, May 27-29, 2014, Electronic Proceedings in Theoretical Computer Science 151, pp. 370–381.
Research supported by the Czech Science Foundation grant GA14-10799S.
Published: 21st May 2014.

ArXived at: bibtex PDF

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