TeV Physics from the Top Down

Abstract

Concrete semi-realistic string/M theory constructions often predict the existence of new physics at the TeV scale, which may be different in character from the bottom-up ideas that are motivated by specific problems of the standard model. I describe two examples, heterotic and open string, of such constructions. The latter has a particularly interesting strongly-coupled quasi-hidden sector, which may lead to composite states at low energy and dynamical supersymmetry breaking. General issues, such as grand unification versus direct compactification, additional U(1)' gauge symmetries and other exotics, and flat directions are discussed.