Quenched approximation

In particle physics, quenched approximation is an approximation often used in lattice gauge theory in which the quantum loops of fermions in Feynman diagrams are neglected. Equivalently, the corresponding one-loop determinants are set to one. This approximation is often forced upon the physicists because the calculation with the Grassmann numbers becomes relatively awkward in lattice gauge theory.

Most of the recent calculations avoid the quenched approximation.