# From Effective Lagrangian to Feynman Rule

1. Apr 5, 2015

### zhangyang

In this process:

N*→N+photon

If we want to calculate the amplitude with the following interaction Lagrangian:

(http://arxiv.org/abs/nucl-th/0205052)

If we use functional method,the field operator is not polynomial,how to use "center formula"to bring functional derivative in? Or we must drop functional method,and use expension of field operator into annihilation and creation operator to get amplitude ?

2. Apr 5, 2015

### Einj

I honestly don't know how to write the Feynman rules for such a Lagrangian with the path integral formalism. Personally I always found much easier to simply use the canonical expression for the fields and from there write down the rules starting from the creation and annihilation operators.