Editing AdS/CFT correspondence (section)

=== Quantum field theory ===

{{Main|Quantum field theory|Conformal field theory}}

The application of quantum mechanics to physical objects such as the [[electromagnetic field]], which are extended in space and time, is known as [[quantum field theory]].{{refn|A standard text is {{harvnb|Peskin|Schroeder|1995}}.}} In [[particle physics]], quantum field theories form the basis for our understanding of elementary particles, which are modeled as excitations in the fundamental fields. Quantum field theories are also used throughout condensed matter physics to model particle-like objects called [[quasiparticle]]s.{{refn|For an introduction to the applications of quantum field theory to condensed matter physics, see {{harvnb|Zee|2010}}.}}

In the AdS/CFT correspondence, one considers, in addition to a theory of quantum gravity, a certain kind of quantum field theory called a [[conformal field theory]]. This is a particularly [[symmetric]] and mathematically well-behaved type of quantum field theory.{{refn|Conformal field theories are characterized by their [[Invariant (physics)|invariance]] under [[conformal map|conformal transformations]].}} Such theories are often studied in the context of string theory, where they are associated with the [[worldsheet|surface]] swept out by a string propagating through spacetime, and in [[statistical mechanics]], where they model systems at a [[critical point (thermodynamics)|thermodynamic critical point]].{{refn|For an introduction to conformal field theory emphasizing its applications to perturbative string theory, see Volume II of Deligne et al. 1999.}}