# Feynman rules for anomalous vertex [closed]

We can read Feynman rules directly from the lagrangian in the simplest cases, but for the following lagrangian I am a few stuck

$\mathcal{L}=4g\phi\epsilon^{\mu\nu\rho\sigma}\partial_{\mu}A_{\nu}\partial_{\rho}A_\sigma$,

with $A_{\mu}$ the e.m field, $\phi$ a neutral, scalar spin-less field, $g$ a coupling. After conventionally assign momentum and indexes to external legs, what is the quickest way to find the rule?

## closed as off-topic by rob♦Jul 13 '18 at 22:23

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• Taking functional derivatives is the usual way to find vertex rules. And remember derivatives give rise to factors of momentum. – JamalS Jun 28 '18 at 8:07