Notes on Local Grand Unification

Abstract

Grand unified models in four dimensions typically suffer from the doublet-triplet splitting problem. This obstacle can be overcome in higher-dimensional settings, where a non-trivial gauge group topography can explain the simultaneous appearance of complete standard model generations in the form of 16-plets of SO(10) and the Higgs fields as split multiplets. In these notes, the emerging scheme of `local grand unification' and its realization in the context of orbifold compactifications of the heterotic string are reviewed.

Based on lectures given at the Summer Institute 2007, Fuji-Yoshida, Japan. The slides can be found at http://wwwhep.s.kanazawa-u.ac.jp/SI2007/slides/ratz.pdf