All Questions
Tagged with quantum-field-theory feynman-diagrams
1,156
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How might you quantise this non-polynomial action?
I am interested in the following non-polynomial action:
$$L = \sqrt{(\partial_\mu \phi \partial^\mu \phi^2 + m^2 \phi^2 -\lambda^2\phi^4)^2 + \varepsilon^2 } dx^2 $$
where $\varepsilon$ is very small....
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Understanding Feynman Diagrams in Loop Corrections to the propagator $\phi ^3 $ theory [closed]
I found other posts talking about the same chapter in the same book, but none of them were exactly about what I am asking here.
In Srednicki's chapter 14 (Loop corrections to the propagator), we are ...
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2PI Effective Action from Double Legendre Transformation
This answer (https://physics.stackexchange.com/q/348673) provides good intuition for why Legendre transformation induces 1-particle irreducible graphs:
It mainly tries to convey the idea that the ...
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Feynman rule for scalar QED vertex
A popular problem in QFT textbooks and courses is to derive the Feynman rules for scalar QED. Usually, this theory is presented via the following Lagrangian density:
$$\mathcal{L} = (D_\mu\phi)^\...
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Making Feynman Diagrams for a given process
I do not have much experience in field theory so please do suggest a text or source where I can find detailed explanation for my question.
My question is, how to draw feynman diagram for a given ...
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Proper time of two particles being the same when they are under a tree-level interaction
I have a question: I have a figure like this:
The interpretation of the diagram is this: a particle is emitted at $x_2$, interacts with the field at $x_1$ and from $x_1$ another particle is emitted ...
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Determining if Self-Energy is Complex from Action Alone?
My understanding of quantum field theory is that an interacting two-point function of spin-0 bosons will have the form: $ \frac{i}{p^2-m_0^2-\Sigma(p)}$, where $\Sigma(p)$ is the self-energy, the sum ...
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How can I calculate the cross section in general?
How can I calculate the cross-section of a process with three possible Feynman diagrams? I usually see examples with only the scattering amplitude defined by the $t$ channel, but if the scattering ...
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Why does an all connected diagram contribute to two-point function?
I am recently reading E.Witten's review for $1/N$ expansion of QCD. In there, considering the main contribution of quark bilinears like $\bar{q}q$, then He mentions that in free field theory there is ...
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Confused with the product of Feynman propagators [closed]
While reading Thomas Rauh's 'Introduction to Feynman integrals and multiloop techniques' I came across the following identity $$\frac{1}{A^aB^b}=K\int^1_0 \frac{dx x^{a-1}(1-x)^{b-1}}{[xA+(1-x)B]^{a+b}...
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How to derive momentum-space Feynman rules from position-space ones?
I was reading Peskin-Schroeder's QFT text (P-S) and came across Equation (4.47) stating the vertex factor when four lines meet. P-S says
the $z$-dependent factors of the diagram is: $$ \int d^4z\,e^{-...
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Feynman rule from dynamical Chern-Simons
Consider the following action that
\begin{equation}
S = \int d^4x\sqrt{-g}\left(-\frac{1}{2}(\partial\phi)^2 + V(\phi) + \frac{2R}{\kappa^2}
- \frac{\phi}{4f}{}^*RR\right)
\end{equation}
where
\...
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Feynman diagrams in string theory
I am beginning to study string theory, I have a beginner level doubt:
If we consider a Feynman torus diagram in string theory, it is a worldsheet. What does it represent? Does it actually mean that in ...
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Exact definition of topological non-identical diagrams
It is often said that Feynman diagrams for fermions do not have symmetry factors.
Consider I have a spinless fermionic quantum many-body system with Hamiltonian:
$$H=\int_{r}\psi^{\dagger}(r)\frac{\...
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Textbook for Feynman Diagrams
I need to get an understanding of Feynman diagrams, something I currently have basically no knowledge of, and I am looking for a good textbook/place to start. I have finished my 3rd year undergrad, ...