Abstract: "In this paper time-bounded auxiliary push-down automata (AuxPDA), i.e. time and space bounded Turing machines with additional push-down store, are considered. We investigate the power of unambiguous Aux-PDA, i.e., machines that have at most one accepting computation, and ambiguity bo...

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Bibliographische Detailangaben

Hauptverfasser:	Niedermeier, Rolf 19XX- (VerfasserIn), Rossmanith, Peter (VerfasserIn)
Format:	Buch
Sprache:	English
Veröffentlicht:	München 1990
Schriftenreihe:	Technische Universität <München>: TUM 9054
Schlagworte:	Turing machines
Zusammenfassung:	Abstract: "In this paper time-bounded auxiliary push-down automata (AuxPDA), i.e. time and space bounded Turing machines with additional push-down store, are considered. We investigate the power of unambiguous Aux-PDA, i.e., machines that have at most one accepting computation, and ambiguity bounded AuxPDA. Recently, it was shown by Buntrock, Hemachandra, and Siefkes that space bounded Turing machines, whose computation trees have moderate ambiguity, can be efficiently simulated by by unambiguous AuxPDA with same space bound. This paper shows that such an efficient simulation is also possible for AuxPDA. The simulation incorporates no space and time penalty, unless the ambiguity is very high By similar methods it is shown that unambiguous AuxPDA can efficiently simulate a certain class of unambiguous, semi-unbounded fan-in circuits, which answers an open question posed by Lange. Finally, obliviousness for AuxPDA is considered and it is proved that unambiguous AuxPDA work w.l.o.g. with a very limited amount of space on the push-down store, a result that is already known for deterministic and nondeterministic AuxPDA.
Beschreibung:	38 S.