Superstring Phenomenology and Large Extra Dimensions

The recent understanding of string theory opens the possibility that apparent weakness of gravitational interactions can then be accounted by the existence of large internal dimensions, in the submillimeter region. Furthermore, our world must be confined to live on a brane transverse to these large dimensions, with which it interacts only gravitationally. This scenario gives a new theoretical framework for solving the gauge hierarchy problem and the unification of all interactions. It has dramatic implications for observations at future particle colliders, such as production of Kaluza-Klein states and graviton emission in the bulk of extra dimensions. It also predicts a radical change of gravitational forces in the submillimeter range, which can be measured in non-accelerator gravity experiments.