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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How exactly does a proton form from quarks? What is the exact sequence and mechanism?
What are the steps that lead to the bonding of two up quarks and one down quark into a proton? For instance, does an up quark "bind" with a down quark in quark-gluon plasma, which then binds ...
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Probability amplitudes in Richard Feynman’s QED [duplicate]
So i’ve been reading Richard Feyman’s book, QED, and in it, he simplifies the idea of how physicists calculate the probability of a photon hitting a certain detector. He lets the magnitude of a vector ...
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Why does light interact with normal matter but not with other light?
Why does light interact with normal matter but not with other light?
Assumptions:
Light does not interact with other light at all.
Light does interact with other matter, i.e reflection/refraction.
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Why did Schwinger [Phys. Rev. 74 (1948) 1439] choose a non-standard form of the Lagrangian density associated with the free electromagnetic field?
This sounds like a science history question, but is not. It is about acceptable forms for the Lagrangian density of electromagnetism. There is also a second question on the distinction between total ...
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Why poles of two-point function corresponds to bound states?
In this article Two-time Green function method in quantum electrodynamics of high-Z few-electron atoms the author has:
Let $\mathcal{G}$ be fourier transform of the green function
$$
\begin{array}{r}
\...
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Are static electric and magnetic fields flows of virtual photons? [duplicate]
Many electromagnetic interactions are modeled as exchanges of a real photons: e.g. an excited electron can relax and emit a photon. Somewhere else, a photon and an electron can interact, "...
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Spin magnetic dipole moment of electron not an invariant with acceleration?
Since the energy of the electron at rest can be calculated by:
$$
E_e=\frac{h c}{ \lambda_e}
$$
where $\lambda_e$ is the Compton wavelength value of the electron at rest, $h$ the Planck constant and $...
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Unitarity of time-evolution operator of Dirac's equation
Let $\Psi(t)$ be state of Dirac's electron in context of Dirac's equation and consider time-evolution operator
$$\Psi(t) = U(t)\Psi(0)$$
is or is not $U$ an unitary (preserving length) operator?
(note ...
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Lorentz invariance
In QED loop renormalization, Lorentz invariance is often used to express the possible momentum-dependence of the propagators.
For example, the propagator corresponding to the fermion loop is
$$ie_0^2 \...
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Radiative correction of the electron self-energy
In Mandl & Shaw's Quantum Field Theory (2nd edition p217), the radiative correction for the electron self-energy is:
$$
e_0^2 \Sigma(p) =
\frac{\tilde{e_0}^2}{16\pi^2} (p\!\!/ -4m) \left(\frac{2}{\...
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Why would energy conservation be violated during interference if a wave function represented multiple photons?
the below paragraph is from Paul Dirac's 'The principles of quantum mechanics'. He argues that representing multiple photons' probability distribution via a single wavefunction leads to energy ...
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Propagator and Ward identity in the $R_\xi$ gauge
The full gauge propagator in the $R_\xi$ gauge is
$$D_{\mu\nu} = \frac{i}{k^2+i\epsilon}\left(-g_{\mu\nu}+\frac{1-\xi}{k^2}k_\mu k_\nu\right).\tag{1}$$
Now if we take $\xi=0$, we get the Lorenz gauge, ...
