Twistor string theory

Twistor string theory was proposed by Edward Witten in 2003.

Twistor theory was introduced by Roger Penrose in the 1960s and is an approach at the unification of quantum theory with gravity. Penrose proposed that twistor space should be the underlying geometric background on which physical theories are defined. He also proposed that spacetime itself together with its physical fields should emerge from twistor space. Twistor space is a 3-dimensional complex projective space. In twistor space, physical quantities appear as certain structural deformations. Spacetime and the familiar spacetime fields emerge as a consequence of this description. Spacetime itself, together with conventional physical fields, must emerge from these deformed complex structures. Calculations on twistor space give the same as on spacetime. They are often:

• Simpler

• Manifest the full natural symmetries

• Are dramatically more efficient

Twistor space is chiral. Left and right handed objects are treated differently. For example, the graviton (gravity) and the gluon (strong nuclear force) are both right handed. 

In 2003, Edward Witten, a leading developer of string theory, produced a ground-breaking paper showing how string theory can be introduced into twistor space. This would provide a full physical model that incorporates both right and left-handed fields and their full interactions. 

The most important contribution of twistor string theory has been particle collision scattering amplitudes. These determine the probabilities of potential scattering processes. Edward Witten showed that the simple structure that they would have in twistor space. This has allowed a better understanding of experimental observations in particle colliders. It has also allowed a deeper insight into the nature of different QFTs. The insights that have emerged from twistor string theory have led to new insights in pure mathematics, such as:

• Grassmannian residue formulae

• The amplituhedron

• Holomorphic linking