We give a characterization of hypercyclic finitely generated abelian
semigroups of matrices on C^n using the extended limit sets (the J-sets).
Moreover we construct for any n\geq 2 an abelian semigroup G of GL(n;C)
generated by n + 1 diagonal matrices which is locally hypercyclic but not
hypercyclic and such that JG(e_k) = C^n for every k = 1; : : : ; n, where (e_1;
: : : ; e_n) is the canonical basis of C^n. This gives a negative answer to a
question raised by Costakis and Manoussos.Comment: 10 page