# Contact Term and Schwinger Term

In field theory, when 4-divergences of time-ordered Green's functions are computed, there are extra terms known as 'Schwinger terms'.

When deriving the quantum equations of motion for time-ordered Green's functions, there are extra terms known as 'Contact terms'.

Are contact terms and Schwinger terms one and the same? Or is one a special case of the other? Or are they completely unrelated things? [There's also some kind of relationship with $\mathcal{L}_\text{int}\neq\mathcal{H}_\text{int}$, when I can't place my finger on.]

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Suggestion to the question (v1): While you are at it, you could also ask about 'Seagull terms'. – Qmechanic Apr 6 '13 at 23:16