  We study the dynamics of the massive Schwinger model on a lattice using exact
diagonalization. When periodic boundary conditions are imposed, analytic
arguments indicate that a non-zero electric flux in the initial state can
"unwind" and decrease to a minimum value equal to minus its initial value, due
to the effects of a pair of charges that repeatedly traverse the spatial
circle. Our numerical results support the existence of this flux unwinding
phenomenon, both for initial states containing a charged pair inserted by hand,
and when the charges are produced by Schwinger pair production. We also study
boundary conditions where charges are confined to an interval and flux
unwinding cannot occur, and the massless limit, where our results agree with
the predictions of the bosonized description of the Schwinger model.
