The (low-energy) physics of the superstring

Abstract

Superstring theories offer the prospect of a finite unified theory of the four fundamental interactions. However, their implications for low-energy physics are difficult to determine because there must be several stages of symmetry breaking leading from the underlying multidimensional supersymmetric string theory, relevant at the scale of string structure (not more thanO(10-32cm)), to the four-dimensional non-supersymmetric effective field theory relevant for physics at scales probed in the laboratory (not less thanO(10-15cm)). I discuss these stages of compactification, supersymmetry breaking and gauge-symmetry breaking and show how the resulting low-energy theory may closely approximate the observed structure. The implications for the multiplet structure, the masses and the couplings of the observed particle states are considered.