We show that emptiness is undecidable for alternating one-way two head finite automata operating on unary input. This solves an open problem posed by Geidmanis. Further we show that a conjecture by King concerning the hierarchy of languages accepted by alternating one-way multi head finite automata does not hold. We also consider closure properties of the languages accepted by these devices and obtain as consequences that the Boolean closures of linear and general context-free languages axe contained in the lower levels of the hierarchy. Some Other simulation techniques axe outlined.
CITATION STYLE
Petersen, H. (1995). Alternation in simple devices. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 944, pp. 315–323). Springer Verlag. https://doi.org/10.1007/3-540-60084-1_84
Mendeley helps you to discover research relevant for your work.