I believe in the book the formula on page 281:
$$
\square_{\alpha\beta}^k \square_{\mu\nu} \langle A_\nu(x)...A_\beta(x_k)...\rangle = \langle j_\mu(x)...j_\alpha(x_k)...\rangle \tag{14.152}
$$
is missing an ##e## factor on the RHS, this seems to be confirmed by the Schwinger-Dyson equation...
I am self-studying QFT in the Schwartz book "Quantum Field Theory and the Standard Model", currently I am struggling to understand the all-orders proof that ##Z_1=Z_2## using Ward-Takahashi identity (page 352).
He states that ## -ie_R\Gamma^\mu ##, which is the sum of the 1PI contributions to...
I graduated in Physics about 25 years ago, and over the years, alongside family and work commitments, I’ve continued to study the areas of physics that interest me. I’m currently studying Quantum Field Theory."