Nonmass Eigenstates of Fermion and Boson Fields

It appears natural to consider the four dimensional relativistic massive field as a five dimensional massless field. If the fifth coordinate is interpreted as the proper time, then the fifth moment can be understood as the rest mass. After introducing the rest mass operator, we define the mass eigenstate and the nonmass eigenstate. The general equations of spin 0, spin 1/2 and spin 1 fields are obtained respectively. It is shown that the Klein-Gordon equation, the Dirac equation and the Proca equation describe the mass eigenstates only. The rest mass of spin 1/2 field and the rest mass squared of Boson fields are calculated. The U(1) gauge field that couples to the nonmass eigenstates is studied carefully, whose gauge boson can be massive.