Landau gauge photon propagator
= Landau gauge photon propagator
{c}
{title2=$D^L_{\mu\nu}=-i(\eta_{\mu\nu}-k_\mu k_\nu/k^2)/(k^2+i0)$}
The <covariant Landau gauge> propagator is the transverse limit of the <inversion of the gauge-fixed Maxwell kinetic operator>. Contracting with $k^\mu$ gives zero away from the pole. The <Lorenz gauge> condition still has residual transformations satisfying $\Box\chi=0$, so boundary conditions and the pole prescription complete the choice.