DISCUSSING THE U(1)-PROBLEM OF QED(2) WITHOUT INSTANTONS

We construct QED(2) with mass and flavor and an extra Thirring term. T he vacuum expectation values are carefully decomposed into clustering states using the U(1)-axial symmetry of the considered operators and a limiting procedure. The properties of the emerging expectation functi onal are compared to the proposed theta-vacuum of QCD. The massive the ory is bosonized to a generalized Sine-Gordon model (GSG). The structu re of the vacuum of QED(2) manifests itself in symmetry properties of the GSG. We study the U(1)-problem and derive a Witten-Veneziano-type formula for the masses of the pseudoscalars determined From a semiclas sical approximation. (C) 1996 Academic Press, Inc.