Juan Barandiaran, Martin Rivas

The spinning electron-electron interaction is described in classical terms by means of two possible classical interactions: The instantaneous Coulomb interaction between the charge centers of both particles and the Poincar\'e invariant interaction developed in a previous work. The numerical integrations are performed with several Mathematica notebooks that are available for the interested readers in the reference Section. One difference of these interactions is that the Poincar\'e invariant interaction does not satisfy the action-reaction principle in the synchronous description and, therefore, there is no conservation of the mechanical linear momentum. It is the total linear momentum of the system what is conserved. In this synchronous description the interaction is not mediated by the retarded fields but is described in terms of the instantaneous positions, velocities and accelerations of the center of charge of both particles. In the Poincar\'e invariant description the net binding force that holds linked two Dirac particles is stronger than in the Coulomb case, thus forming a stable spin 1 system of 2 Dirac particles. This bosonic state of spin 1 does not correspond to a Cooper pair because the separation between the centers of mass of the Dirac particles is below Compton's wavelength, smaller than the correlation distance of the Cooper pair. Since the Poincar\'e invariant interaction is relativistically invariant it can be used for analyzing high energy scattering processes.