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Abstract

The success of the Higgs mechanism in the standard model has led to the
speculation that the standard model gauge group might arise through an
analogous breaking of a yet more unified group. Such `grand unified theories'
have the advantage of unifying both the gauge structure and fermion
representations of the standard model. Unfortunately, the theories that most
elegantly unify the fermions, without predicting extra unobserved fermion
states, do not explain the existence of the three fermion generations. They
also typically predict a proliferation of bosonic states, which lead to so-far
unobserved processes like proton decay. In this paper we introduce an
alternative explanation for why one might only observe a subgroup of a larger
`unified' group in nature. The approach we introduce gives rise naturally to a
generation structure without the appearance of unwanted fermion states, and is
cleaner in the sense that it avoids the usual proliferation of unobserved
bosonic states and resulting unobserved processes.