%0 Journal Article
%T On the structure of the energy-momentum and the spin currents in Dirac's electron theory
%A F. W. Hehl
%A A. Mac¨Şas
%A E. W. Mielke
%A Yu. N. Obukhov
%J Physics
%D 1997
%I arXiv
%X We consider a classical Dirac field in flat Minkowski spacetime. We perform a Gordon decomposition of its canonical energy-momentum and spin currents, respectively. Thereby we find for each of these currents a convective and a polarization piece. The polarization pieces can be expressed as exterior covariant derivatives of the two-forms $\check M_\alpha$ and $M_{\alpha\beta}=-M_{\beta\alpha}$, respectively. In analogy to the magnetic moment in electrodynamics, we identify these two-forms as gravitational moments connected with the translation group and the Lorentz group, respectively. We point out the relation between the Gordon decomposition of the energy-momentum current and its Belinfante-Rosenfeld symmetrization. In the non-relativistic limit, the translational gravitational moment of the Dirac field is found to be proportional to the spin covector of the electron.
%U http://arxiv.org/abs/gr-qc/9706009v1