All Questions
Tagged with quantum-electrodynamics feynman-diagrams
252
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Calculating a Feynman diagram with the helicity basis
In the book by Peskin and Schroeder, they calculate the leading order diagram for the process $e^- e^+ \to \mu^- \mu^+$ (see page 136 for the labelling of the momenta). They do this in two ways: using ...
- 291
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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:
$$\mathcal{L} = (D_\mu\phi)^\...
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Feynman diagrams in Yukawa interaction
I want to understand drawing Feynman Diagrams better, therefore I wanted to draw some for the Lagrangian with a Yukawa interaction term:
$$L = \bar{\psi}(i \partial\!\!\!/ - m)\psi - g \bar{\psi}\phi \...
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Why is $F_1(0) = 1$? (form factor in QED)
In section 6.2 in Peskin and Schroeder (P&S) on vertex corrections, it is shown (eq 6.34) that the physical charge of the electron is given by $eF_1(0)$ (as shown by comparing the nonrelativistic ...
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What is a correlation function of renormalized currents in QED?
The correlation function
$$
\langle\beta|\mathcal{T}J(x_1)\cdots J(x_n)|\alpha\rangle,\tag{1}
$$
where $J^\mu=e\bar{\psi}\gamma^\mu\psi$ is the QED current, is usually interpreted as the diagram of ...
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A question on IR divergence in Peskin-Schroeder chapter 6
In equation 6.64 of Peskin Schroeder, it computes $f_{\text{IR}}(q^2)$ in the limit $-q^2\to\infty$. Now, if we try to simplify the integral:
\begin{align}
f_{\text{IR}}(q^2) &=\int_0^1d\xi\;\frac{...
3
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Some integrals in QED Renormalisation
I am currently leaning the renormalisation of QED and I have met some tricky integral that seems unsolvable. The integrals are shown in Quantum Field Theory and the Standard Model by Schwartz, page ...
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How can I count diagrams (in this scalar QED example) at a particular order without drawing all the Feynman diagrams?
Here's a 3-loop diagram for light-by-light scattering in scalar QED (from Schwartz textbook question 9.2):
The question 9.2 asks approximately how many other diagrams contribute at the same order in ...
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Feynman rule: proton-proton-photon versus electron-electron-photon QED vertex
If the Feynman rule for the vertex is written as $$-ieQ\gamma^\mu$$ ($e>0$, charge of positron, $Q$ is the charge of the interacting particle in units of $e$), the electron-electron-photon QED ...
- 11.7k
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Is Feynman's Compton scattering diagram the same as the one in most books?
Feynman used the following Compton scattering diagram:
Whereas most books use this diagram in their derivation:
Is there a way to relate the two? Feynman's diagram makes more sense to me ...
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Confusion about the dressed propagator
When considering interactions, the free propagator $S_0(p)$ of fermions for example gets "dressed" due to the self-energy of the fermion. The complete propagator then becomes
$$
S(p)=\frac{/\...
- 172
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Interpreting Feynman diagram of Coulomb scattering of positron
I am trying to understand Coulomb positron scattering. This course explains that:
Here the incoming state is in the future and is to be interpreted as a negative-energy electron of four-momentum $-...
- 132
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Deriving Feynman rules for scalar QED
I am a bit confused about Matthew D. Schwartz's statement of the Feynman rules in scalar QED (chapter 9, section 9.2 titled Feynman rules for scalar QED. The Lagrangian is
\begin{equation}
\mathcal{L} ...
- 904
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Are QED Feynman diagrams readable in any order?
I have somewhat of a basic question regarding QED Feynman diagrams. To expose my doubts let's take the Feynman diagram of the Compton scattering (at the second order) as an example:
With the solid ...
- 4,577
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Energy Conservation in Pair Annihilation and Feynman-Stuckelberg Interpretation
The textbook "Modern Particle Physics" by Mark Thomson on p. (98) reads:
In the left plot, an electron of energy $E$ emit a photon with energy $2E$ and, to conserve energy, produces an ...
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