Retrieving the missed particle-antiparticle degrees of freedom of Dirac particles

摘要

The missed particle-antiparticle degrees of freedom are retrieved and thecorresponding particle-antiparticle intrinsic space are introduced to study thedynamical symmetry of the Dirac particle. As a result, theparticle-antiparticle quantum number appears naturally and the Dirac particlehas five quantum numbers instead of four. An anti-symmetry (different from theconventional symmetry) of the Dirac Hamiltonian and a dual symmetry of itseigenfunctions are explored. The $\hat{\kappa}$ operator of the Dirac equationin central potentials is found to be the analog of the helicity operator of thefree particle--the alignment of the spin along the angular momentum.