  Elementary electronic excitations, which are due to the Coulomb-field
scatterings, present the diverse phenomena in 3D, 2D, 1D-nanotube electron
gases, graphene and carbon nanotubes. The critical mechanisms cover the
dimension-dependent bare Coulomb potentials, energy dispersions, and
free/valence carrier density. They are responsible for the main features, the
available excitation channels (the electron-hole regions), the joint van Hove
singularities, the undamped/damped collective excitations at small/sufficiently
high transferred momenta, the momentum dependences of plasmon frequencies
(acoustic and optical modes), and their categories (the intraband and
inter-pi-band plasmons). There exists certain significant similarities and
difference among various systems. The (momentum/ angular momentum,
frequency)-excitation phase diagrams are directly reflected in the propagation
of plasma waves.
