Equations of motion for spinning particles in external electromagnetic and gravitational fields

Karl Yee, Myron Bander
1993 Physical Review D, Particles and fields  
The equations of motion for the position and spin of a classical particle coupled to an external electromagnetic and gravitational potential are derived from an action principle. The constraints insuring a correct number of independent spin components are automatically satisfied. In general the spin is not Fermi-Walker transported nor does the position follow a geodesic, although the deviations are small for most situations.
doi:10.1103/physrevd.48.2797 pmid:10016525 fatcat:jfex5r5f6jcmfiuoa2mrep5hlu