  Cylindrical surface plasmon (CSP) mode coupling in a nanowire or a
nanochannel is described in terms of three-dimensional Kaluza-Klein theory in
which the compactified third dimension is considered to be the angular
coordinate of the metal cylinder. Higher (n>0) CSP modes are shown to posses a
quantized effective charge proportional to their angular momentum n. In a
nanowire these slow moving charges exhibit strong long-range interaction via
fast massless CSPs with zero angular momentum (n=0). Such a mode-coupling
theory may be used in description of nonlinear optics of cylindrical nanowires
and nanochannels (for example, in single-photon tunneling effect), and may be
further extended to describe interaction of electrons with nonzero angular
momenta in thin gold wires and carbon nanotubes
