From the standard model to M-theory: The development of string theory

Abstract

String theory is now the most competitive theory of quantum gravity, and it takes an important role in theoretical physics. In this article, we introduced why we need string theory and how string theory is formed. The importance of string theory is described through general relativity and the Standard Model of particle physics. String theory is originally discovered to describe strong interaction. While a better model for strong interaction was developed, string theory was found to be a candidate for a theory about quantum gravity. The first version of string theory is the bosonic string theory, which was constructed in 26-dimensional space and used to describe bosons. After supersymmetry was introduced, the dimensions were reduced to 10, and the theory is hence called the superstring theory. In the first superstring revolution, 5 different superstring theories were constructed and compactified on the 6-dimensional Calabi-Yau manifold. In the second superstring revolution, the idea of different dualities was introduced in string, as well as D-branes. Hence, it was found that the 5 different superstrings can be unified to get the 11-dimensional M-theory.