- #1
Nixom
- 16
- 0
i just wonder why we call it "sum rule"?
waht do we sum, and what sum for?
waht do we sum, and what sum for?
A QCD sum rule is a theoretical tool used in quantum chromodynamics (QCD), the theory that describes the strong nuclear force. It is used to calculate properties of hadrons, which are particles made of quarks and gluons, such as their masses and decay rates.
A QCD sum rule makes use of the operator product expansion (OPE), which breaks down a complicated operator into simpler ones that can be calculated using perturbative QCD. The OPE is then related to physical observables through the dispersion relation, resulting in a sum rule.
QCD sum rules are limited by the accuracy of the OPE and the validity of the dispersion relation. They also require a large amount of experimental data to be reliable.
QCD sum rules have been used to study a variety of hadronic properties, such as masses, decay rates, and form factors. They have also been applied to the calculation of strong interaction parameters, such as the strong coupling constant.
Lattice QCD is a numerical technique for solving QCD on a discrete space-time grid. QCD sum rules can be used to validate and improve the lattice QCD calculations by providing an independent theoretical approach to calculating hadronic properties.