Questions tagged [quantum-electrodynamics]
Quantum electrodynamics (QED) is the quantum field theory believed to describe electromagnetic interaction. It is the simplest example of a quantum gauge theory, where the gauge group is abelian, U(1).
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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 ...
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Looking for a graph of the running of the electron mass
Is there a graph somewhere showing how the electron mass changes with energy due to renormalization up to around the Planck scale - assuming that the pure standard model is always valid (thus no GUT, ...
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How to distinguish a doppler-shifted photon from a non-doppler-shifted photon of the same frequency?
Can one physically distinguish a photon of frequency $\omega$, generated by a stationary laser, from a photon generated by a mechanically moving laser (a different laser from the first one) which, due ...
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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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Is completeness relation of polarization vector equivalent to propagator?
For the Proca Lagrangian:
$$\mathcal{L}=-\frac{1}{4}F_{\mu \nu}F^{\mu \nu}+\frac{1}{2}m^{2}A_{\mu}A^{\mu}$$
the equation of motion is:
$$\Box A^{\mu}-\partial^{\mu}\partial_{\nu}A^{\nu}+m^{2}A^{\mu}=0$...
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Derivation of the quantization of the EM field in a dielectrics
I'm currently studying the quantization of the EM field in a dielectric medium and trying to understand the quantization scheme of Huttner and Barnett (1992, see Phys. Rev. A 46, 4306). The system ...
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Tightly-focusing a single photon
I'm curious about the feasibility, both theoretically and experimentally, of tightly focusing (or spatially trapping) a single photon to guarantee its precise targeting. If it’s possible, isn’t it ...
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The relative phase of photons in two-photon absorption
In two-photon absorption (TPA), the relative polarization of the two photons about to be absorbed simultaneously by an atom is crucial in determining the TPA rate. However, there is a lack of ...
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Charge renormalization choice in QED
In the lectures on QFT I'm following we define the renormalized QED Lagrangian as
$$\mathcal{L} = \dfrac{1}{4} (F_0)_{\mu\nu} (F_0)^{\mu\nu} + \bar{\psi}_0 (i \bar{\partial} - (m_0)_e) \psi_0 - e_0 \...
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How particles interact with the electromagnetic potential $A^\mu$?
It is well known that one reason quantum mechanics started to being developed, was because scientist wanted a model to explain electron orbits in atoms.
Borh interpreted that the for orbits to exist ...
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Ward identity in scalar QED; gauge transformations & plane wave solutions for polarization
I am prepping for my QFT2 exam tomorrow, and in one of the mock exams I found the following question (and I'm not quite sure how to go about this). Given the following Lagrangian:
$$
L = -\frac{1}{4}...
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Why are these terms not present in the QED Lagrangian?
I am working though some questions for my QFT/ QED exam and i am having trouble with the following question:
Explain why the following terms cannot be part of the Lagrangian of QED:
$-g(\bar{\psi}\...
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Are EM waves telling us the probability of finding a photon?
I feel like I've been frequently presented with an interpretation of EM waves that goes something like this:
Light is an oscillating electromagnetic field. Because changes in the electric field ...
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QED impact on Unified Field Theory [closed]
how did the development of quantum electrodynamics impact the development of modern unified field theories?
and did any other theories have more significant impact?
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Commutation behavior of spinors in Feynman diagrams
I am currently playing around with computing cross sections of several simple interactions in QED like Bhabha and Compton Scattering and I have stumbled upon a question which I havent yet managed to ...
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