Abstract
The fermion mixing transformations are studied in the quantum field theory framework. In particular neutrino mixing is considered and the Fock space of definite flavor states is shown to be unitarily inequivalent to the Fock space of definite mass states. The flavor oscillation formula is computed for two and three flavors mixing and the oscillation amplitude is found to be momentum dependent, a result which may be subject to experimental test. The flavor vacuum state exhibits the structure of
SU(2)
generalized coherent state.