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This was the first definition of string theory that was fully non-perturbative and a concrete mathematical realization of the holographic principle. It is an example of a gauge-gravity duality and is now understood to be a special case of the AdS/CFT correspondence.
Twistor string theory is an equivalence between N = 4 supersymmetric Yang–Mills theory and the perturbative topological B model string theory in twistor space. [1] It was initially proposed by Edward Witten in 2003. Twistor theory was introduced by Roger Penrose from the 1960s as a new approach to the unification of quantum theory with gravity.
Perturbation theory also fails to describe states that are not generated adiabatically from the "free model", including bound states and various collective phenomena such as solitons. [citation needed] Imagine, for example, that we have a system of free (i.e. non-interacting) particles, to which an attractive interaction is introduced ...
As a string travels through spacetime it traces out a surface, called the worldsheet of the string. Unfortunately, the moduli space of such parametrized surfaces, at least a priori , is infinite-dimensional; no appropriate measure on this space is known, and thus the path integrals of the theory lack a rigorous definition.
In string theory, the strings may be open (forming a segment with two endpoints) or closed (forming a loop like a circle) and may have other special properties. [1] Prior to 1995, there were five known versions of string theory incorporating the idea of supersymmetry (these five are known as superstring theories) and two versions without supersymmetry known as bosonic string theories, which ...
The problem of developing a non-perturbative formulation of string theory was one of the original motivations for studying the AdS/CFT correspondence. [37] As explained above, the correspondence provides several examples of quantum field theories that are equivalent to string theory on anti-de Sitter space.
[1] [2] A critical feature of the technique is a middle step that breaks the problem into "solvable" and "perturbative" parts. [3] In regular perturbation theory, the solution is expressed as a power series in a small parameter . [1] [2] The first term is the known solution to the solvable problem.
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.