Abstract:
We propose here a variant of the super-cell systems (also called, for
short, P systems), which looks less restrictive (more realistic) than the variants
investigated so far. In P systems as introduced in [7] (see a survey in [8]), the use
of objects evolution rules is regulated by a given priority relation; moreover, each
membrane has a label and one can send objects to precise membranes, identified
by their labels. We get rid of both there rather artificial (non-biochemical) features. Instead, we add to membranes and to objects an \electrical charge" and
the objects are passed through membranes according to their charge. We prove
that such systems are able to characterize the one-letter recursively enumerable
languages (equivalently, the recursively enumerable sets of natural numbers),
providing that an extra feature is considered: the membranes can be made
thicker or thinner (also dissolved, as in [7]) and the communication through
a membrane is possible only when its thickness is equal to 1. Several open
problems are formulated.