Representation mixing for SU₃ and G₂

Abstract

A theory whose exact invariance with respect to SU₃ is broken by interactions transforming like the hypercharge generator of SU₃ is studied in perturbation theory. Physical particle states corresponding to unperturbed SU₃ multiplets are obtained by mixing into these multiplets possible impurities corresponding to other SU₃ multiplets, these impurities being as general as the perturbation allows. The effect of symmetry breaking on various physical quantities like masses and magnetic moments can then be obtained in terms of mixing parameters, and interesting formulas follow various restrictions of their values. Similar considerations applied to G₂ show that many of the conclusions which made exact G₂ invariance unattractive remain for approximate G₂ invariance.