# Questions tagged [1pi-effective-action]

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### Feynman rules for space-dependent coupling

Let's say I have an effective action which looks like (I got this action from large $N$ method for $\varphi^4$ theory): $$\int \frac{d^4x}{2g}\phi^2(x)+\int d^4x \ \log(-\nabla^2+\mu^2+i\phi(x)).$$ ...
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### Must the mean field, in the context of the background field method, satisfy the classical equations of motion?

When deriving the effective action $\Gamma$ in the background field method, one splits the field $\phi = \phi_b + \phi_f$ into a background (or mean field) $\phi_b$ and fluctuations $\phi_f$, then ...
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### 1-loop Correction

Given a Lagrangian: $$L = \frac{1}{2}(\partial_u\phi)^2 + g (\partial_u\phi)^4.$$ Does anyone have idea how to write down the 1-loop correction? The derivative coupling is the part that confuses me.
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### What happens to the (Wilsonian) effective action if a symmetry is spontaneously broken?

A spontaneously broken symmetry is a symmetry of the action which does not manifest itself in physical states. Since the action is still invariant under this symmetry, can we say the same about the ...
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### Definition of one-particle irreducible diagrams

Text books often defines one-Particle Irreducible diagram (1PI diagram) as a connected diagram which does not fall into two pieces if you cut one internal line. Is this internal line the full ...
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### Effective potential in scalar-vector interaction

I am reading the thesis of Erick James Weinberg from arXiv: https://arxiv.org/abs/hep-th/0507214. On page 22 he finds the effective potential in scalar-vector interaction in one-loop. I am having a ...
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141 views

### How to find the CP violating effective operator?

I've been meeting with one not-very-small problem in arriving at (3.3) in Shaposhnikov's "Structure of the high temperature gauge ground state and electroweak production of the barygon asymmetry" (...