Quark-Antiquark Bound States in an Extended QCD_2 Model
  We study an extended QCD model in 2D obtained from QCD in 4D by compactifying two spatial dimensions and projecting onto the zero-mode subspace. This system is found to induce a dynamical mass for transverse gluons -- adjoint scalars in QCD(2), and to undergo a chiral symmetry breaking with the full quark propagators yielding non-tachyonic, dynamical quark masses, even in the chiral limit. We construct the hadronic color singlet bound-state scattering amplitudes and study quark-antiquark bound states which can be classified in this model by their properties under Lorentz transformations inherited from 4D. 
Pedro Labrana (1), Jorge Alfaro (1), Alexander A. Andrianov (2) ((1)   Universidad Cat\'olica de Chile, (2) St. Petersburg S...