Minimal parallelism for polarizationless P systems

Minimal parallelism was recently introduced [3] as a way the rules of a P system are used: from each set of applicable rules associated to the same membrane, at least one must be applied. In this paper, we consider the minimal parallelism for P systems with active membranes without polarizations, using additional features, such as separation operations, changing membrane labels, catalytic or cooperative rules, etc. With several combinations of such features we obtain computational completeness. In cases where membrane division (of elementary or non-elementary membranes) is allowed, we show how SAT can be solved in polynomial time.