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 heads, neither of which is on $, are more t...
