Correlation function (quantum field theory): Difference between revisions

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For non-scalar theories the reduction formula also introduces external state terms such as polarization vectors for photons or spinor states for fermions. The requirement of using the connected correlation functions arises from the [[cluster decomposition]] because scattering processes that occur at large separations do not interfere with each other so can be treated separately.<ref>{{cite book|first=S.|last=Weinberg| author1-link=Steven Weinberg|title=The Quantum Theory of Fields: Volume 1Foundations| publisher=Cambridge University Press| date=1995| chapter=6|volume=1| page=270| isbn=9780521670531}}</ref>

==See also==