 Landau gauge (quantum field theory)

The $\xi \to 0$ limit of covariant gauge fixing by $-({\partial }_{\mu }{A}^{\mu }{)}^2/(2\xi )$. It imposes the divergence condition sharply and gives a transverse photon propagator. This is distinct from the vector-potential choice called Landau gauge for a uniform magnetic field when computing Landau levels.