All Questions
Tagged with quantum-electrodynamics quantum-spin
61
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Elastic scattering and conservation of spin
I am trying to understand conservation of spin in QED elastic scattering in these nice notes (VJ Martin, Particle Physics, Spring 2012, University of Edinburgh): https://www2.ph.ed.ac.uk/~vjm/Lectures/...
- 184
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2
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Understanding attractive/repulsive boson-mediated forces based on interference of free-space fields
I just worked through the derivations of the Yukawa interaction for scalar and spin one particles (i.e. Peskin and Schroeder, end of chapter 4, which covers the tree-level Feynman diagram). It's very ...
- 2,504
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How to correctly interpret $\hat{\sigma}_{eg}^i \hat{\sigma}_{ge}^j$?
I am trying to figure out the paper of Asenjo-Garcia et al.: PHYS. REV. X 7, 031024 (2017).
Specifically, in e.g. Equation (5):
$$ \mathcal{H}_{eff} = -\mu_0 \omega_0^2 \sum_{i,j = 1}^N \mathbf{D}^* \...
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Question on Spinor choice in QED
In QED (see Peskin and Schoeder's book on QFT or Srednicki's book), to determine the fermion wave-function, we usually start with a spinor of a massive particle that is not moving, say
$$u_+(\vec{p}=\...
- 3,992
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Total Angular Momentum operator in spinor-helicity formalism
I am reading Evidence for a new Soft Graviton theorem, by Cachazo and Strominger. At some point, they express the relation
$$J_{\mu\nu}\sigma^{\mu}_{\alpha\dot{\alpha}}\sigma^{\mu}_{\beta\dot{\beta}}
=...
- 3,992
3
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290
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Understanding the factorization of subleading soft contributions-massless QED
I am reading The SAGEX Review on Scattering Amplitudes Chapter 11: Soft Theorems and Celestial Amplitudes. In subsection 2.2, the subleading soft photon theorem is derived. The result is
$$A^{\mu}=\...
- 3,992
2
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133
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Frenkel or Tulczyjew-Dixon Condition and QED
What is the physical motivation behind imposing Frenkel's condition,
$$p_{\mu}S^{\mu\nu}=0$$
for an electron of momentum $p$ and spin given by some tensor $S^{\mu\nu}$?
In addition, a direct ...
- 3,992
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102
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Covariant Spin Operator for Massless Fermions
I have been reading the paper The Covariant Definition Of Spin in Relativistic QFT by Hilgevoord and De Kerf, in which the authors derive the spin operator in relativistic quantum theories of free ...
- 3,992
4
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Can bremsstrahlung, cyclotron radiation, or Larmor radiation flip the spin of a particle?
There are many situations where a photon is emitted from a charged particle because it accelerates. This includes bremsstrahlung, which is usually a charged particle scattering of a nucleus and losing ...
- 7,434
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130
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Is there a theoretical justification for using $\vec{F}_{\text{loop}} = \nabla(\vec{\mu}\cdot\vec{B})$ as the force on a particle due to spin?
We know elementary particles have magnetic dipole moments and thus they react to magnetic fields. However, it turns out that the force on a magnetic dipole depends on the choice of model of the ...
- 8,660
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Can one extend the explanations in Feynman's book "QED" to include spin?
Feynman's book QED is wonderful. Somewhere at the beginning, he writes that he does not take into consideration spin.
Is there a paper, a text or an explanation similar to that beautiful book but ...
3
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1
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100
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Ability of electrons to spin or rotate vs Spin Quantum Number
I know that the Spin Quantum Number is NOT necessarily some kind of measure of the rotation of an electron. I guess they chose that name when they realized an electron has a magnetic field around it ...
- 33
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How can the same virtual particle both attract and repel charged particles together?
so I've read a lot of things about QED and stuff, and I've clearly understood that charged particles are in fact "charged" because they exchange virtual photons, small packets of energy with ...
- 21
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Weak Interaction (leptons to boson)
I'm going through a practice exam and saw this question.
Q: Which ONE of the following is an allowed weak interaction process?
I eliminated the possible answers to the following two.
$e^+$ + $\nu_e$ -...
- 59
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113
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Where, exactly, does the boundary lie between 'entangled' particles and merely 'interacting' or 'coupled' ones?
Have scientists discovered, yet, the precise amount of interaction needed to actually 'entangle' a pair or more of particles, beyond mere interaction or even coupling?
Is there a distinct difference, ...
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