Multitape finite automata with rewind instructions

Quantum Finite Multitape Automata

Quantum finite automata were introduced by C. Moore, J. P. Crutchfield [MC 97], and by A. Kondacs and J. Watrous [KW 97]. This notion is not a generalization of the deterministic finite automata. Moreover, in [KW 97] it was proved that not all regular languages can be recognized by quantum finite automata. A. Ambainis and R. Freivalds [AF 98] proved that for some languages quantum finite automa...

The Equivalence Problem of Multitape Finite Automata

Using a result of B.H. Neumann we extend Eilenberg’s Equality Theorem to a general result which implies that the multiplicity equivalence problem of two (nondeterministic) multitape finite automata is decidable. As a corollary we solve a long standing open problem in automata theory, namely, the equivalence problem for multitape deterministic finite automata. The main theorem states that there ...

Revisiting the Equivalence Problem for Finite Multitape Automata

The decidability of determining equivalence of deterministic multitape automata (or transducers) was a longstanding open problem until it was resolved by Harju and Karhumäki in the early 1990s. Their proof of decidability yields a co-NP upper bound, but apparently not much more is known about the complexity of the problem. In this paper we give an alternative proof of decidability, which follow...

Size Reduction of Multitape Automata

The equivalence problem of multidimensional multitape automata

This article considers the equivalence problem of multitape automata with multidimensional tapes, where the motion of the heads is monotone in all directions (no backward motion). It is shown that this problem can be reduced to the equivalence problem of ordinary multitape automata. Some applications of the result are adduced. © 2008 Elsevier Inc. All rights reserved.