Bethe-Salpeter Equations with Instantaneous Confinement: Establishing Stability of Bound States

Abstract: Salpeter equations with potential functions rising to infinity in configuration space do not automatically predict stable bound states. For this to happen, also the Lorentz behaviour of the involved Bethe-Salpeter kernels is crucial. At least for interaction potentials of harmonic-oscillator form analytic scrutinies of Salpeter equations with confining interactions may identify those Bethe-Salpeter kernels which describe bound states free from the notorious instabilities encountered in numerical evaluations. Such truly confining kernels can be singled out systematically by requesting the resulting bound-state energy spectra to be both real and discrete.