Abstract
Electronic states of carbon nanotubes in a magnetic field perpendicular to the axis are studied in a tight-binding model and the validity of k·p theory is examined.The energy bands near the Fermi level calculated in the tight-binding model agree with those of k·p in a wide magnetic-field range except in extremely high fields where the flux passing through the unit cell of a two-dimensional graphite is comparable to the flux quantum, i.e. up to --4000 T.A slight deviation from the k·p result in weak magnetic fields can be explained by the inclusion of higher order terms in the k·p expansion leading to trigonal warping of bands.
