Li Zhifeng (Vienna):
Stability in the instantaneous Bethe-Salpeter formalism: Harmonic-oscillator reduced Salpeter equation
A popular three-dimensional reduction of the Bethe-Salpeter
formalism for the description of bound states in quantum field theory is the Salpeter equation, derived
by assuming both instantaneous interactions and free propagation of all bound-state constituents.
Numerical (variational) studies of the Salpeter equation with confining interaction, however, observed
specific instabilities of the solutions, likely related to the Klein paradox and rendering (part of the)
bound states unstable. An analytic investigation of this problem by a comprehensive spectral analysis
is feasible for the reduced Salpeter equation with only harmonic-oscillator confining interactions.
There we are able to prove rigorously that the bound-state solutions correspond to real discrete energy
spectra bounded from below and are thus free of any instabilities.