New answers tagged quantum-electrodynamics
2
votes
Is there any radiation similar to Bremsstrahlung in electron-electron or electron-positron scattering?
You are comparing apples and oranges. You show the tree diagram, but there are also radiative diagrams:
which are higher order, and hence fall under "radiative corrections".
In practice, ...
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0
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Is there any radiation similar to Bremsstrahlung in electron-electron or electron-positron scattering?
I believe there is Bremsstrahlung in electron-electron scattering, but it is small at low energies because the dipole moment of a system of two electrons is zero in the reference frame where the ...
- 27.5k
0
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Quantum description of radio antenna
How Energy States Appear in an Antenna (Idea)
Here’s a possible quantum mechanical view of how antennas work, focusing on plasmon modes. This is just a developing idea:
Collective Electron Behavior:
...
2
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Functional derivative of gauge fixing condition - Peskin QFT page 295
Hints:
Functional/variational differentiation
$$\frac{\delta\alpha(x)}{\delta\alpha(y)}=\delta^4(x\!-\!y)$$
here acts on different/independent spacetime points $x$ and $y$; not the same spacetime ...
- 213k
2
votes
Accepted
Can photons be seen in a superconductor?
Great question! :) My next video will cover this in depth.
It's a nuanced topic. Basically what happens is that the superconducting condensate can be described by a complex scalar field psi (Ginzburg-...
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1
vote
Accepted
Pole structure of the photon polarisation tensor
On one hand, $\Pi^{\mu\nu}(q)=(q^2g^{\mu\nu}-q^{\mu}q^{\nu})\Pi_2(q^2)$ in eqs. (7.72)-(7.75) is the renormalized 1PI photon vacuum polarization/self-energy.
On the other hand, $\Pi^{\mu\nu}(q)=(q^2g^...
- 213k
1
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Can photons be seen in a superconductor?
Yes, photons gain a mass in a superconductor, but it also means that the EM field decay very quickly when it tries to enter a superconductor. For that reason, it is very difficult to get a photon ...
- 15.8k
1
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Phase Space Integral For Compton Scattering COM Frame
As explicitly stated on p. 162 of Peskin-Schroeder, they are computing the Compton scattering cross section in the laboratory frame (where $\vec{p}=0$ and $E=m$) and not in the center of mass (COM) ...
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0
votes
Accepted
Relativistic corrections to Mandelstam variable $t$
I think I should first address the main misconception here. The Mandelstam variables are defined in a relativistic framework, therefore there can be no relativistic corrections to them. What the book ...
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Scattering into collection of bound states: relativistic vs non-relativistic case
The computation of $S$-matrix elements, say, in QED and $\phi^4$ theories in all standard textbooks I looked shows that one always computes scattering amplitudes of a bunch of free particles to ...
- 65k
2
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What is predicted to happen for electron beams in the Stern-Gerlach experiment?
In 2015, someone did this experiment. The electron beam does split!
Observing the spin of free electrons in action(Stern-Gerlach experiment by free electrons)
I'll quote a paragraph in the result of ...
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3
votes
Are angular momentum selection rules only understood for hydrogen like species?
I know for certain, that the same selection rules apply for Yb, Sr and Mg atoms, which have two valence electrons.
Since the selection rules are consequences of angular momentum conservation, they ...
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6
votes
Accepted
Are Stokes parameters Lorentz invariant?
For simplicity, let's consider a plane monochromatic wave propagating in $\hat z$ direction. If we parametrize the Stokes parameters in terms of the propagating electric field (see Born and Wolf, ...
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Photon propagator and the Fermi Lagrangian density
It is quite possible to use the Fermi Lagrangian as a starting point of classical electromagnetic field theory. Here is my paper on this. It is correct that the resulting theory is not gauge invariant....
- 26.6k
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Question about fermion self-energy and on-shell renormalization
I will attempt to answer my question for two reasons: first, to see if I have understood correctly the comment of @Triatticus and, second, to have a clear answer so that other people can see. So, ...
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