X iv : h ep - t h / 93 01 01 3 v 1 5 J an 1 99 3 Fermionic Determinant of the Massive Schwinger Model

A representation for the fermionic determinant of the massive Schwinger model, or QED 2 , is obtained that makes a clean separation between the Schwinger model and its massive counterpart. From this it is shown that the index theorem for QED 2 follows from gauge in-variance, that the Schwinger model's contribution to the determinant is canceled in the weak field limit, and that the determinant vanishes when the field strength is sufficiently strong to form a zero-energy bound state.