Gauge theories in a bag Original Research Article

We investigate multi-flavour gauge theories confined in (d = 2n)-dimensional/euclidean bags. The boundary conditions for the ‘quarks’ break the axial-flavour symmetry and depend on a parameter θ. We determine the θ-dependence of the fermionic correlators and determinants and find that a CP-breaking θ-term is generated dynamically. As an application we calculate the chiral condensate in multi-flavour QED2 and the abelian projection of QCD2. In the second model a condensate is generated in the limit where the number of colours, Nc tends to infinity. We prove that the condensate in QCD2 decreases with increasing bag radius R at least as R−1/NcNf. Finally we determine the correlators of mesonic currents in QCD2.