The Family Group in Grand Unified Theories

Abstract

We review the known ways of incorporating and breaking symmetries in a renormalizable way. We summarize the various grand unified theories based on $S{U}_5,S{O}_{10}$, and $E_6$ as family enlargement groups. An $S{U}_5$ model with an $S{U}_2$ gauged family group is presented as an illustration. In it, the e-family (i.e., e,u and d) is classically massless and acquires calculable mass corrections. The family group is broken by the same agent that does the superstrong breaking. Finally, we sketch a way of unifying the family group with $S{U}_5$ into $S{U}_8$.

Comments: Retro-Preprint (1979 unpublished Caltech preprint). Uses tex, with jnl macro, 19 pages. Invited talk at the Sanibel Symposia, Feb 1979