  In the late 1990's, M. Gromov introduced the notion of mean dimension for a
continuous map, which is, as well as the topological entropy, an invariant
under topological conjugacy. The concept of metric mean dimension for a
dynamical system was introduced by Lindenstrauss and Weiss in 2000. In this
paper we will verify which properties coming from the topological entropy map
are valid for both mean dimension and metric mean dimension. In particular, we
will prove that the metric mean dimension map is not continuous anywhere on the
set consisting of continuous maps on both the Cantor set, the interval or the
circle. Finally we prove that the metric mean dimension on the set consisting
of continuous map on the interval and on the circle is not lower
semi-continuous.
