Affiliations: Research Group on Mathematical Linguistics, Rovira i
Virgili University, Pl. Imperial Tàrraco 1, 43005 Tarragona, Spain | Department of Computer Science, University of Western
Ontario, London, Ontario, Canada N6A 5B7 | Institute of Mathematics of the Romanian Academy, PO
Box 1-764, 70700 Bucureşti, Romania | Leiden Institute of Advanced Computer Science, Leiden
University, Niels Bohrweg 1, 2333 CA Leiden, The Netherlands
Abstract: This paper continues research on membrane systems which function by
communication only, meaning that there are no evolving rules for molecules. The
whole computation process relies on passage of molecules through membranes --
this provides communication between regions of the membrane system. Next to
transport of single molecules through membranes (uniport) we also study a
coupled transport of molecules, with two molecules passing either in the same
direction (symport) or in opposite directions (antiport). We study the
computational power of such membrane systems and prove that using only symport
one gets Turing universality. Moreover, we prove that five membranes suffice to
get Turing universality, and the number of membranes can be decreased to three
if forbidding context conditions for transport are used.
