Sum rules (quantum field theory)

In quantum field theory, a sum rule is a relation between a static quantity and an integral over a dynamical quantity. Therefore, they have a form such as: ∫ A ( x ) d x = B {\displaystyle \int A(x)dx=B} where A ( x ) {\displaystyle A(x)} is the dynamical quantity, for example a structure function characterizing a particle, and B {\displaystyle B} is the static quantity, for example the mass or the charge of that particle.

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