Simple GUTs

Abstract

Together with some positive features, such as the constrained hypercharge assignments, grandunification models typically have some unwelcome aspects, mostly associated with the rich and peculiarly selected matter content. I discuss some ideas which might help to interpret (part of) this apparent complexity arising in grandunification in terms of simple structures. I also point out that the conventional criteria used to establish fine tuning in grandunified models should be modified if these models are viewed as effective low-energy descriptions of a more fundamental theory.