Nicholas Q. Trân

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It is well known that programs using only the following constructs: {x+x+ 1, X+-.X I 1, if x =0 then goto I, goto 1, halt} compute all partial recursive functions [7]. In fact, Minsky showed that simple programs with three variables compute all partial recursive functions with one argument and, consequently, simple programs with three variables recognize(More)
We continue the study of the computational power of synchronized alternating Turing machines (S.4 T.M) introduced in (Hromkovi? 1986, Slohodob$ 1987. 19883. h) IO allow communication via synchromzation among processes of alternating Turing machines. We are interested m comparing the four main clasbcs of space-bounded synchronized alternating Turing-machines(More)
Given an n-tape nondeterministic finite automaton (NFA) M with a one-way read-only head per tape and a right end marker $ on each tape, and a nonnegative integer k, we say that M is weakly ksynchronized if for every n-tuple x = (x1, . . . , xn) that is accepted, there is a computation on x such that at any time during the computation, no pair of input(More)
We continue the study of communication-bounded synchronized alternating finite automata (SAFA), first considered by Hromkovič et al. We show that to accept a nonregular language, an SAFA needs to generate at least Ω(log logn) communication symbols infinitely often; furthermore, a synchronized alternating finite automaton without nondeterminism (SUFA) needs(More)