Covariance and uniqueness of the canonical fermion coherent state.

Abstract

A unitary Fock-space operator that leaves the canonical quantization rule for fermions covariant is introduced. The defining equation of a canonical fermion coherent state retains the symmetry under this unitary transformation. This fact mandates that the coherent state must accompany a partner state, and that the form of a state in the pair is related to the partner state by the symmetry. A careful definition of the phase in the extended fermion Fock space is crucial for the uniqueness of the normalized fermion coherent state. Also the proper choice of the phase renders the canonical fermion coherent state equal to a displaced-vacuum state