"Grand Unification In Four And More Dimensions, And In Strings"

Abstract:

 

The standard model of particle yields an excellent description of measurements at collider experiments. Yet it contains a large number of continuous parameters that have to be adjusted to fit observations. On the other hand, the structure of the standard model hints at a simpler scheme. In particular, grand unified theories (GUTs) provide us with a more elegant framework by unifying the symmetries and the matter content of the standard model.

In the talk, I will discuss the virtues and problems of GUTs, such as proton decay. I will argue that the problems can only be overcome with extra dimensions. I will then discuss how the corresponding higher-dimensional GUTs are realized in explicit string-derived models, which reproduce the (supersymmetric) standard model. Finally I will comment on how one may
conceivably probe such stringy models of particle physics in future experiments.