Shape vibrations of topological fermions
  We analyze the model of topological fermions, where charged fermions are treated as topological solitons. We discuss vibrations of soliton shapes. It is shown that depending on the power of the potential term (discrete parameter m) of the model Lagrangian the spectrum of normal mode frequencies can be discrete (for m = 1) or continuous (for integer m > 1). 
Manfried Faber, Alexander Kobushkin, Mario Pitschmann