Correlation function
In
statistics and
probability, in particular in
stochastic processes, the value of a
correlation function r(
s,
t) is the
correlation between
random variables Xs and
Xt, where the indices
s and
t are often either points in time or physical locations.
A caveat, though, in quantum field theory, we sometimes have nonpositive states and in that case, a probabilistic interpretation makes no sense. At any rate, even in ordinary quantum field theory, we need to work with quantum probability instead of classical probability.
See also
This is a stub article. Ideally, it will make clear that the correlation functions in astronomy, financial market analysis, etc., are all instances of the same idea; therefore, a disambiguation page is not what this should be.