Journal of the ACM (JACM)
Reversal-Bounded Multicounter Machines and Their Decision Problems
Journal of the ACM (JACM)
Symbolic String Verification: An Automata-Based Approach
SPIN '08 Proceedings of the 15th international workshop on Model Checking Software
Symbolic String Verification: Combining String Analysis and Size Analysis
TACAS '09 Proceedings of the 15th International Conference on Tools and Algorithms for the Construction and Analysis of Systems: Held as Part of the Joint European Conferences on Theory and Practice of Software, ETAPS 2009,
Relational string verification using multi-track automata
CIAA'10 Proceedings of the 15th international conference on Implementation and application of automata
On synchronized multitape and multihead automata
DCFS'11 Proceedings of the 13th international conference on Descriptional complexity of formal systems
Multitape NFA: weak synchronization of the input heads
SOFSEM'12 Proceedings of the 38th international conference on Current Trends in Theory and Practice of Computer Science
How to synchronize the heads of a multitape automaton
CIAA'12 Proceedings of the 17th international conference on Implementation and Application of Automata
On the open problem of Ginsburg concerning semilinear sets and related problems
Theoretical Computer Science
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Given an n-tape automaton M with a one-way read-only head per tape which is delimited by an end marker $ and a nonnegative integer k, we say that M is weakly k-synchronized if for every n-tuple x=(x1, …, xn) that is accepted, there is an accepting computation on x such that no pair of input heads, neither of which is on $, are more than k tape cells apart at any time during the computation. When a head reaches the marker, it can no longer move. As usual, an n-tuple x=(x1, …, xn) is accepted if M eventually reaches the configuration where all n heads are on $ in an accepting state. We look at the following problems: (1) Given an n-tape automaton M, is it weakly k-synchronized for a given k (for some k)? and (2) Given an n-tape automaton M, does there exist a weakly k-synchronized automaton for a given k (for some k) M′ such that L(M′)=L(M)? In an earlier paper [1], we studied the case of multitape finite automata (NFAs). Here, we investigate the case of multitape pushdown automata (NPDAs), multitape Turing machines, and other multitape models. The results that we obtain contrast those of the earlier results and involve some rather intricate constructions.