  Based on the Schwinger-Dyson (SD) equation, the fermion mass generation is
further studied in the D(2<D<4)-dimensional Thirring model as a gauge theory
previously proposed. By using a certain approximation to the kernel, we
analytically obtained explicit form of the dynamical mass of fermion and the
critical line in (N,1/g) space, where N is the number of fermions and g is the
dimensionless vector-type four-fermion coupling constant. This analytical
result is confirmed by the numerical solution for the SD equation with exact
form of the kernel in (2+1) dimensions.
