LNCS 2950 - Aspects of Molecular Computing (Frontmatter Pages)

20 Artiom Alhazov, Carlos Martín-Vide, and Linqiang Pan
E ′ . At same time the other copy of q exits the membrane, changing its
polarization to neutral.
14. [ 2yi → yi+1] 0
2 , 1 ≤ i ≤ n − 1.
15. [ zi → zi+1]
2 0
, 1 ≤ i ≤ n − 1.
2
16. [ 2ei,j,0 → es(i),s(j),0] 0
2 , 1 ≤ i, j ≤ n, where s(t) =min(t +1,n+2).
17. [ 2gi → gi+1] 0
2 , 0 ≤ i ≤ n − 1.
18. [ 2zn → p] 0
2 .
19. [ 2yn] 0
2 → [ +
2 ] 2 u.
At step n +2k +7,yi,zi (1 ≤ i ≤ n − 1) evolve to yi+1,zi+1, g0 evolves to
g1, zn evolves to p, ei,j,0 (1 ≤ i, j ≤ n) evolvetoes(i),s(j),0, wheres(t) =
min(t +1,n+ 2); at same time, yn exits the membrane where it appears,
changing the polarization of that membrane to positive.
20. [ 2ei,n+1,0 → u] +
2 , 1 ≤ i ≤ n +1.
21. [ 2en+1,i,0 → u] +
2 , 1 ≤ i ≤ n +1.
22. [ 2p] +
2 → [ 0
2 ] 2u. In the membranes with label 2 and positive polarization (i.e., the membranes
where yn appear in the last step, this means that vertex vn does not belong
to the corresponding subset), ei,n+1,0 and en+1,i,0 (1 ≤ i ≤ n +1)evolveto
u (which will never evolve again); at the same time, object p exits the membrane,
returning the polarization of the membrane to neutral (this makes
possible the use of rules of types 14, 15, 16, 17, 18, and 19).
In the membranes with label 2 and neutral polarization (i.e., the membranes
where yn do not appear in the last step, this means that vertex vn belongs
to the corresponding subset), using rule of type 16, ei,n+1,0 and en+1,i,0
(1 ≤ i ≤ n+1) evolvetoei+1,n+2,0 and en+2,i+1,0 (this means that the edges
ei,n and en,i do not belong to V × (V − A) ∪ (V − A) × V ,whereAis the
corresponding subset).
The rules of types 14, 15, 16, 17, 18, 19, 20, 21, and 22 are applied as many
times as possible (in one step rules of types 14, 15, 16, 17, 18, and 19, in
the next one rules of types 20, 21, and 22, and then we repeat the cycle).
In this way, after 2n steps, a membrane will contain an object en+2,n+2,0
if and only if that membrane contains an edge which does not belong to
V × (V − A) ∪ (V − A) × V ,whereAis the corresponding subset. In the
following steps, we will let the membranes corresponding to a positive answer
send out an object.
23. [ 2gn → gn+1q] 0
2 .
24. [ 2gn+1 → gn+2] 0
2 .
25. [ 2gn+2 → gn+3] −
2 .
26. [ en+2,n+2,0]
2 −
2 → [ +
] 2 2 u.
27. [ 2gn+3] −
2 → [ −
2 ] 2 yes.
28. [ yes] 1 0
1 → [ +
] 1 1 yes.
At step 3n +2k +7,gn evolves to gn+1q. Atstep3n +2k +8,gn+1 evolves
to gn+2, and at the same time, object q exits the membrane, changing the
polarization to negative (using rule of type 4). At step 3n +2k +9,inthe