On a Classical, Geometric Origin of Magnetic Moments, Spin-Angular   Momentum and the Dirac Gyromagnetic Ratio
  By treating the real Maxwell Field and real linearized Einstein equations as being imbedded in complex Minkowski space, one can interpret magnetic moments and spin-angular momentum as arising from a charge and mass monopole source moving along a complex world line in the complex Minkowski space. In the circumstances where the complex center of mass world-line coincides with the complex center of charge world-line, the gyromagnetic ratio is that of the Dirac electron. 
Ezra T. Newman