Conserved-current two-point function
= Conserved-current two-point function
{title2=$G(k^2)$}
In a massless four-dimensional theory, current conservation gives a transverse tensor structure, $\int d^4x\,e^{-ikx}\langle J_\mu(x)J_\nu(0)\rangle=(k_\mu k_\nu-\delta_{\mu\nu}k^2)G(k^2)$. With current <mass dimension> three, the scalar coefficient has dimension zero.