Quantum Field Theory of Particles with Both Electric and Magnetic Charges

The quantum field theory of particles with both electric and magnetic charges is developed as an obvious extension of Schwinger's quantum field theory of particles with either electric or magnetic charge. Two new results immediately follow. The first is the chiral equivalence theorem which states the unitary equivalence of the Hamiltonians describing the system of particles with electric and magnetic charges e₍, g₍ and the system with charges {e₍}^'=cos, e₍+sing₍, {g₍}^'=-sine₍+cosg₍. This result holds in particular in the absence of physical magnetic charges. The second result is that if physical magnetic charges do occur, then, in consequence of chiral equivalence, the charge quantization condition applies, not to the separate products e₌g₍, but to the combinations e₌g₍-g₌e₍, which must be integral multiples of 4. The general solution of this condition leads to the introduction of a second elementary quantum of electric charge e₂, the electric charge on the Dirac monopole, besides the first elementary charge e₁, the charge on the electron. There are no other free parameters.