Klein-Gordon and Dirac gyroscopes
  The formulation of a rigid body in relativistic quantum mechanics is studied. Departing from an alternate approach at the relativistic classical level, the corresponding Klein-Gordon and Dirac operators for the rigid body are obtained in covariant form. The resulting wave equations are shown to be consistent, by construction, with earlier definitions of a relativistic rigid body by Aldinger et al (1983). Wave functions and spectra for both cases are obtained explicitly, including the Dirac gyroscope with asymmetries. 
Emerson Sadurni