  The electronic states of capped semi-infinite nanotubes are studied within
the phenomenological gauge field-theory model. A single manifold for the
description of both the nanotube and the cap region (considered as nearly a
half of either Ih or I fullerene) is suggested. The wavefunctions and the
density of states (DoS) are numerically calculated for both metallic and
semiconducting nanotubes. The smoothing of van Hove singularities is found and
proven analytically. The comparison with the experimental observations is
discussed.
