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## Main Question or Discussion Point

**Quantum Field Theory Purly in Momentum Space???**

Hello,

I have a complicated nonlinear-nonlocal-nonrelativistic-effective action in momentum space and would like to do perturbation theory with that. I need to find propagator and Feynman rules. I can not go to x-space and follow the standard procedure of finding the equation of motion and inverting it to get the propagator.

Has anyone seen any quantum field theory that was purely done in momentum space from the action to the perturbation?

I would appreciate it if you could show me a reference or an idea?

Thanks