Higher-derivative two-dimensional massive fermion theories

We consider the canonical quantization of a generalized two-dimensional mas sive fermion theory containing higher odd-order derivatives. The requiremen ts of Lorentz invariance, hermiticity of the Hamiltonian and absence of tac hyon excitations suffice to fix the mass term, which contains a derivative coupling. We show that the basic quantum excitations of a higher-derivative theory of order 2N + 1 consist of a physical usual massive fermion, quanti zed with positive metric, plus 2N unphysical massless fermions, quantized w ith opposite metrics. The positive-metric Hilbert subspace, which is isomor phic to the space of states of a massive free fermion theory, is selected b y a subsidiary-like condition. Employing the standard bosonization scheme, the equivalent boson theory is derived. The results obtained are used as a guideline to discuss the solution of a theory including a current-current i nteraction.