Relativistic electron theory: Is spin a property of the electron in vacuo or of the electromagnetic field interaction



Here we investigate electron spin as a property of the electron–magnetic field interaction, rather than as a property of the free electron in the absence of electromagnetic fields. We show that, within the phase of the interaction linear in the vector potential, the Pauli or Dirac magnetic moment interaction Hamiltonian can be derived by using a form of the vector potential that depends on the Pauli spin vector and by consistently using electron and field four-vectors to ensure Lorentz invariance of quantities related to physical observables. The Dirac equation itself is shown to follow from this procedure. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004