Ward-Takahashi Identities, Magnetic Anomalies, and the Anticommutation   Properties of the Fermion-Boson Vertex
  It is well-known that following summing Feynman graphs, the fermion-boson coupling vertex is modified according to gamma^u-->Gamma^u=gamma^u+Delta^u, with Delta^u representing non-divergent perturbative corrections. Here, we calculate the anticommutators specified by Gamma^uv=.5{Gamma^u,Gamma^v}, and then explore some consequences of employing these as a metric tensor g^uv=Gamma^uv(p',q,p) in momentum space. The challenge is that Gamma^u and Gamma^uv must them be introduced in place of gamma^u and n^uv throughout the Lagrangian density, denoted L', resulting in what appears, superficially, to be different physics from what is known and observed. However, with a suitable reparameterization of fermion rest masses m', interaction charges e' and momentum vectors p^u' into their observed counterparts m, e and p^u, it turns out that L' can be made to describe physics identical to that of the customary QED Lagrangian density L at low photon momentum q^u-->0, including the observed magnetic anomaly. That is,we prove that one is able to obtain L(m,e,p^u)=L'(m',e',p^u') for q^u-->0. We find through the Ward-Takahashi identity, as summarized in Figure 2, that interaction vertexes are proportional to the difference between the ordinary and covariant momentum-space derivatives of the metric tensor, and thus an indicator of curvature. Finally, we obtain additional non-longitudinal terms in the Ward-Takahashi relation. 
Jay R. Yablon