 Sum rules (quantum field theory)

In quantum field theory (QFT), "sum rules" refer to relationships or constraints that arise from the principles of quantum mechanics, symmetries of the system, and the structure of the underlying quantum fields. These rules serve to relate various physical quantities and often provide important insights into the properties of particles and interactions. A few important types of sum rules in quantum field theory include: 1. **Sum Rules from Current Algebra**: These arise from the conservation of certain currents in the theory.