Correlation function (quantum field theory)

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In quantum field theory, the (real space) n-point correlation function is defined as the functional average (functional expectation value) of a product of field operators at different positions

For time-dependent correlation functions, the time-ordering operator is included.

Correlation functions are also called simply correlators. Sometimes, the phrase Green's function is used not only for two-point functions, but for any correlators.

  • The correlation function can be interpreted physically as the amplitude for propagation of a particle or excitation between y and x. In the free theory, it is simply the Feynman propagator(for n=2). [For more information see 'An Introduction to Quantum Field Theory' by Peskin & Schroeder, Section 4.2 : Perturbation Expansion of Correlation Functions]

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References[edit]

Books[edit]

  • Alexander Altland, Ben Simons (2006). Condensed Matter Field Theory. Cambridge University Press.