0 a theory that says that the most basic pieces of matter are extremely small lines or circles rather than points --
1 a theory explaining the character of matter and the forces of the universe, based on the idea that they behave more like closed circles of string than like points --
It was this beta function which was apparently found before full string theory was developed.
In string theory, the possibilities are much more constrained, and there are only a few consistent formulations of the theory.
String theory describes how strings propagate through space and interact with each other.
This is fortunate for phenomenology, as phenomenological models often use a physical string theory compactified on a 3 complex-dimensional space.
Consequently, there are no local degrees of freedom in topological string theory.
This is surely an indictment of something, but its relevance to string theory is marginal at best.
Tachyonic fields indeed arise in many versions of string theory.
Recent developments in string theory suggest that the string theory landscape of vacua is vast.
