238 research outputs found
Discussing the U(1)-Problem of QED_2 without Instantons
We construct QED_2 with mass and flavor and an extra Thirring term. The
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 functional are compared to the
proposed theta-vacuum of QCD. The massive theory is bosonized to a generalized
Sine-Gordon model (GSG). The structure 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 semiclassical approximation.Comment: Accepted for publication in Annals of Physic
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