In recent years a new potential symmetry of fundamental particle physics has been investigated—discrete quark-lepton symmetry. When this symmetry is implemented, however, it often leads to either of the unrealistic predictions ${\mathit{m}}_{\mathit{u}}$=${\mathit{m}}_{\mathit{e}}$ or ${\mathit{m}}_{\mathit{d}}$=${\mathit{m}}_{\mathit{e}}$. This paper considers two possible ways models based on ${\mathit{m}}_{\mathit{d}}$=${\mathit{m}}_{\mathit{e}}$ can be made realistic.

• Received 24 October 1994

DOI:https://doi.org/10.1103/PhysRevD.51.6490