  In this paper, we bring together results about the existence of a somewhere
dense (resp. dense) orbit and the minimal number of generators for abelian
semigroups of matrices on $\mathbb{R}^n$. We solve the problem of determining
the minimal number of matrices in normal form over $\mathbb{R}$ which form a
hypercyclic abelian semigroup on R^n. In particular, we show that no abelian
semigroup generated by $[\frac{n+1}{2}]$ matrices on $\mathbb{R}^n$ can be
hypercyclic. ([ ] denotes the integer part). This is a corrected version of the
paper published in Topology and its Applications 210 (2016), 29-45 (see also
[4]). The differences between this version and the published version are
explained at the end of the Introduction.
