## Basic Ideas of Superstring TheoryA string's space-time history is described by functions X
which describe how the string's two-dimensional "world sheet," represented
by coordinates ^{m}(s,t)(s,t), is mapped into space-time
X. There are also functions
defined on the two-dimensional world-sheet that describe other degrees of
freedom, such as those associated with supersymmetry and gauge symmetries.
^{m}Surprisingly, classical string theory dynamics is described by a conformally invariant 2D quantum field theory. (Roughly, conformal invariance is symmetry under a change of length scale.) What distinguishes one-dimensional strings from higher dimensional analogs is the fact that this 2D theory is renormalizable (no bad short-distance infinities).
By contrast, objects with p dimensions, called "p-branes," have a (p+1)-dimensional world volume theory.
For p > 1, those theories are non-renormalizable. This is the feature that gives strings a special status, even though, as we will discuss later, higher-dimensional p-branes do occur in superstring theory.
## Perturbation Theory## Compactification of Extra Dimensions## A Theory of Everything?Previous |Next |

| Contents | Resolving Contradictions | Supersymmetry | A Brief History of Superstings |

| Basic Ideas of Superstring Theory | Superstring Revolution, part deux |