Bound-state spectrum of the SU(2) massive Thirring model

We present the bound-state spectrum of an SU(2) massive Thirring model by employing the 1/K expansion method. For charge-2 sector (qq), the model is found to possess one bound state. For charge-0 sector (qq-bar boson), there are four bound states, one singlet and three triplet bosons. For various combinations of U(1) and SU(2) coupling constants gs and gv, we find some interesting observations. For gs = 0, for example, the binding energy of the triplet boson vanishes again when gv is 4π, which shows a critical point. Also, the charge-2 state and the singlet boson have the same mass spectrum behaviour. For gv 4/3 gs, we find that the charge-2 sector does not have a bound state while the singlet and triplet bosons become just the same boson as the U(1) case. It is still open to interpretation whether these phenomena should be treated in terms of Abelian and/or non-Abelian bosonizations. (Author)