We investigate some generalizations of the Hofstadter problem to higher
dimensions with Abelian and non-Abelian gauge field configurations. We
numerically show the hierarchical structure in the energy spectra with several
lattice models. It is also pointed out the equivalence betwee the \pi-flux
state and the staggered formalism of Dirac fermion.Comment: 1+15 pages, 2 figures; minor corrections, references adde
