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In physics, the Polyakov action is an action of the two-dimensional conformal field theory describing the worldsheet of a string in string theory.It was introduced by Stanley Deser and Bruno Zumino and independently by L. Brink, P. Di Vecchia and P. S. Howe in 1976, [1] [2] and has become associated with Alexander Polyakov after he made use of it in quantizing the string in 1981. [3]
String cosmology is a relatively new field that tries to apply equations of string theory to solve the questions of early cosmology. A related area of study is brane cosmology . Overview
String theory is a theoretical framework that attempts to address these questions. The starting point for string theory is the idea that the point-like particles of particle physics can also be modeled as one-dimensional objects called strings. String theory describes how strings propagate through space and interact with each other.
In 1974, Joël Scherk and John Schwarz suggested that string theory was therefore not a theory of nuclear physics as many theorists had thought but instead a theory of quantum gravity. [53] At the same time, it was realized that hadrons are actually made of quarks, and the string theory approach was abandoned in favor of quantum chromodynamics.
According to superstring theory, or more generally string theory, the fundamental constituents of reality are strings with radius on the order of the Planck length (about 10 −33 cm). An appealing feature of string theory is that fundamental particles can be viewed as excitations of the string.
String field theory (SFT) is a formalism in string theory in which the dynamics of relativistic strings is reformulated in the language of quantum field theory.This is accomplished at the level of perturbation theory by finding a collection of vertices for joining and splitting strings, as well as string propagators, that give a Feynman diagram-like expansion for string scattering amplitudes.
In particle physics and string theory (), the ADD model, also known as the model with large extra dimensions (LED), is a model framework that attempts to solve the hierarchy problem (Why is the force of gravity so weak compared to the electromagnetic force and the other fundamental forces?
In 1990, Edward Witten introduced topological string theory, [14] a simplified version of string theory, and physicists showed that there is a version of mirror symmetry for topological string theory. [28] This statement about topological string theory is usually taken as the definition of mirror symmetry in the mathematical literature. [29]