Abstract.
In the basic variant of P systems, membranes are used as separators and as channels of communication. Other variants, introduced to obtain more "realistic" models, consider membranes with different features: membranes of variable thickness, electrically charged membranes and active membranes (membranes can be divided to create new membranes). These features are not only useful to obtain "realistic"models: we show how we can use them to get simpler and faster models.
This work has been supported by the Italian Ministry of University (MURST), under project "Unconventional Computational Models: Syntactic and Combinatorial Methods".