  The Schwinger model (QED_2) with N flavors of massive fermions on a circle of
circumference L, or equivalently at finite temperature T, is reduced to a
quantum mechanical system of N-1 degrees of freedom. With degenerate fermion
masses (m) the chiral condensate develops a cusp singularity at $\theta=\pm
\pi$ in the limit L -> $\infty$ or T -> 0, which is removed by a large
asymmetry in the fermion masses. Physical quantities sensitively depend on the
parameter mL or m/T, and the m -> 0 and L -> $\infty$ (or T -> 0) limits do not
commute. A detailed analysis is given for N=3.
