String Theory: T-duality

Once, it appeared that there were 5 different string theories. Then in the early-mid 1980's the first superstring revolution occured, and like Buddist monks physicists discovered that the 5 string theories were actually different aspects or descriptions of one underlying theory.

Mathematically, it was discovered that the different string theories were related by dualities. One of these dualities, T-duality, relates a string theory of a small compact dimension on a circle to a string theory of a large dimension. We discuss this in this sample chapter from String Theory Demystified.

Read this doc on Scribd: Strings Chapter 8