 Correlation function (quantum field theory)

In quantum field theory (QFT), the correlation function (also known as the Green's function or propagator) is a fundamental mathematical object that encapsulates the statistical and dynamical properties of quantum fields. Correlation functions are used to relate the values of fields or operators at different points in spacetime and are crucial for understanding the behavior of quantum systems. ### Definition The correlation function typically describes the expectation value of products of field operators at various spacetime points.