Abstract
We investigate the change of Hall conductance induced by band crossing in the Hofstadter spectrum. Numerical study shows that, if the magnetic flux is p/q flux quanta per plaquette, then the change of the Hall conductance is qe 2 /h or 0, depending on whether the energy dispersion near degenerate points is linear or quadratic. This is consistent with an earlier study by Bellissard (cond-mat/9504030, unpublished). We also find that the change of the Hall conductance is accompanied by the "transport" of a daughter subband between the degenerate parent bands. A semiclassical explanation of this subtle effect is offered.