Abstract:
Two-dimensional massless four-fermion theory (1) is considered which includes,
any number of fermionic multiplets in the leading order of $1/N$ expansion. The model is
asymptotically free. At any value of the coupling constant the chiral invariance is dynamically
broken and fermions get masses. For the case of two multiplets at least two
different phases with massive fermions are shown to exist. Conditions are found under
which the theory has no ghosts. Masses of boson states are calculated for the case of
equal fermion masses.