New time hierarchy results for deterministic TMS
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We show a method of maintaining a distributed counter by 2-dimensional deterministic Turing machines with at least two tapes. Our method yields a tight time hierarchy for these machines solving an open problem posed by M. Fürer ([Fü1],[Fü2]). Moreover, we improve the best known time hierarchy theorem for one-tape off-line deterministic TMs; among others we show that this hierarchy is tight for functions bounded by polynomials.
KeywordsTuring Machine Simulated Step Input Word Input Tape Universal Machine
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