Aula Conversi, Roma 1

Using the Wick-Cutkosky model we calculated the bound states in a quantum-field theoretical approach. In the light-front formalism we have calculated the bound-state mass spectrum and wave functions. Using the Terent'ev transformation we can write down an approximation for the angular dependence of the wave function. After calculating the bound-state spectra we characterized all states found. Similarly, we have calculated the bound-state spectrum and wave functions in the instant-form formalism. We compare the spectra found in light-front and instant form dynamics in the ladder approximation and show that in both forms of dynamics the $O(4)$ symmetry of the Wick-Cutkosky model is broken.