Charges and Coupling Strengths in Gauge Theories with Direct Product Symmetry Groups

Abstract

For gauge theories with direct product internal symmetry groups, the relationship between internal quantum numbers (charges) and coupling strengths is examined. In these types of theories, the Lagrangian density may contain non-trivial factors multiplying the matter field terms, and these factors can modify the interaction coupling strengths i.e., the gauge/matter field vertex factors. Consequently, a matter field can carry a given internal charge yet couple to the associated gauge field with an apparent fractional charge. An example with $SU(3)\otimes U(2)$ symmetry is presented in which the matter fields can have integer U(2) charges but fractional U(2) coupling strengths.