  We investigate theoretically perturbations to the confining potential capable
of lifting spin degeneracy in axially symmetric quasi-one-dimensional electron
gases with the spin-orbit interaction. The role of two different types of
perturbations breaking axial symmetry of the system: of non-electromagnetic and
electromagnetic origin is analyzed. We found that these two types of
perturbations have a fundamental distinction in their effects on the energy
spectra. The influence of the scale of perturbation upon the value of spin
splitting is investigated and it is shown that under certain conditions such
splittings can be observed in the experiment.
