Relativistic quark equations, instantaneous interactions and quasi-potentials

In constituent quark model calculations with noncharged quarks, the effective quark mass is small of the order of 300 or 400 MeV which is the order of the internal momenta of the quarks in such calculations. There is thus a need for at least the investigation of relativistic equations, involving such a quark mass in the first place for mass spectrum calculations. This problem is considered. The Salpeter and quasi-potential equations for mesons, wave functions for 0-1 and 1-1 mesons, and potentials and solution methods are studied. A few applications are mentioned. 15 references