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|Title: ||Languages Simultaneously Complete for One-Way and Two-Way Log-Tape Automata|
|Authors: ||Hartmanis, Juris|
Mahaney, Stephen R.
|Keywords: ||computer science|
|Issue Date: ||Feb-1980|
|Publisher: ||Cornell University|
|Abstract: ||In this paper we study languages accepted by nondeterministic $\log n$-tape automata which scan their input only once and relate their computational power to two-way, $\log n$-tape automata. We show that for the one-way, $\log n$-tape automata the nondeterministic model (1-NL) is computationally much more powerful than the deterministic model (1-L); that under one-way, $\log n$-tape reductions there exist natural complete languages for these automata and that the complete languages cannot be sparse. Furthermore, we show that any language complete for nondeterministic one-way $\log n$-tape automata (under 1-L reductions) is also complete for the computationally more powerful nondeterministic two-way, $\log n$-tape reductions. Therefore, for all bounds $T(n),T(n \geq \log n$, the deterministic and nondeterministic $T(n)$-tape bounded computations collapse if the nondeterministic one-way $\log n$-tape computations can be carried out by two-way deterministic $\log n$-tape automata.|
|Appears in Collections:||Computer Science Technical Reports|
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