  Starting from a reformulation of the Thirring model as a gauge theory, we
consider the bosonization of the $D$-dimensional multiflavor massive Thirring
model $(D \ge 2)$ with four-fermion interaction of the current-current type.
Our method leads to a novel interpolating Lagrangian written in terms of two
gauge fields. Especially we pay attention to the case of very massive fermion
$m \gg 1$ in (2+1) and (1+1) dimensions. Up to the next-to-leading order of
$1/m$, we show that the (2+1)-dimensional massive Thirring model is mapped to
the Maxwell-Chern-Simons theory and that the (1+1)-dimensional massive Thirring
model is equivalent to the massive free scalar field theory. In the process of
the bosonization of the Thirring model, we point out the importance of the
gauge-invariant formulation. Finally we discuss a possibility of extending this
method to the non-Abelian case.
