Correlation function (quantum field theory)
For time-dependent correlation functions, the time-ordering operator is included.
Correlation functions are also called simply correlators.
The correlation function can be interpreted physically as the amplitude for propagation of a particle or excitation between y and x.
- Alexander Altland, Ben Simons (2006). Condensed Matter Field Theory. Cambridge University Press.
- Schroeder, Daniel V. and Michael Peskin, An Introduction to Quantum Field Theory. Addison-Wesley.