  The conduction of a single-wall carbon nanotube depends on the pitch. If
there are an integral number of carbon hexagons per pitch, then the system is
periodic along the tube axis and allows "holes" (, and not "electrons",) to
move inside the tube. This case accounts for a semiconducting behavior with the
activation energy of the order of around 3 meV. There is a distribution of the
activation energy since the pitch and the circumference can vary. Otherwise
nanotubes show metallic behaviors. "Electrons" and "holes" can move in the
graphene wall (two dimensions). The conduction in the wall is the same as in
graphene if the finiteness of the circumference is disregarded. Cooper pairs
formed by the phonon exchange attraction moving in the wall is shown to
generate a temperature-independent conduction at low temperature (3-20 K).
