Composite boson dominance in relativistic field theories

We apply a new bosonization technique to relativistic field theories offermions whose partition function is dominated by bosonic composites, andderive the effective action for these bosons. The derivation respects allsymmetries, including gauge invariance, with the exception of Euclideaninvariance which must be checked a posteriori. We use a lattice regularizationwhich should make applications to gauge theories easier. We test the method ona fermion field theory with quartic interaction in the limit when the number offlavours N_f is large, and show that it reproduces the exact results in thebosonic sector, namely condensation of a compositeboson with the right masswhich breaks the discrete chiral invariance of the model. Moreover we determinethe structure function of the condensed composite, whose spatial part turns outto be identical to that of the Cooper pairs of the BCS model ofsuperconductivity.Comment: 34 pages, final versio