Quantum-ElectroDynamics (QED) is the quantum field theory believed to describe the electromagnetic interaction (and with some extension the weak nuclear force).
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Geometrical significance of gauge invariance of the QED Lagrangian
The QED Lagrangian is invariant under
$\psi(x) \to e^{i\alpha(x)} \psi (x)$, $A_{\mu} \to A_{\mu}- \frac{1}{e}\partial_{\mu}\alpha(x)$. What is the geometric significance of this result? Also why is ...
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Feynman Rules for massive vector boson interactions
I am stuck at the beginning of a problem where I am given an interaction term that modifies the regular QED Lagrangian. It involves the interaction between a photon field and a massive vector boson: ...
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Simulation of QED
Can anyone point me to a paper dealing with simulation of QED or the Standard Model in general? I will particularly appreciate a review paper.
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QED Commutation Relations Implications
In Brian Hatfield's book on QFT and Strings there is the following quote:
In particular $$ [A_i (x,t), E_j(y,t)] = -i \delta_{ij}\delta(x-y) $$
implies that $$ [A_i(x,t),\nabla \cdot E(y,t)] = ...
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Is there a simple way to compute some physical constant from Feynman diagram statistics?
I've been playing around writing some software to generate Feynman diagrams for QED, respecting the vertex "rules" described here, and avoiding creating isomorphic duplicates.
So from a starter ...
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When can photon field amplitudes be written as field operators?
Suppose I have some classical field equation for two photon fields with amplitudes $A_1(z),A_2(z)$ (plane waves) given as
${A}_1=\alpha f(A_1,A_2) \\
{{A}_2}=\beta g(A_1,A_2) $
Under what ...
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271 views
Transparency of solids using bandgaps and relation to conduction and valence bands
I think I understand how a solid can appear transparent as long as the energy of the photons travelling through it are not absorbed in the material's bandgap. But how does this band gap relate to ...
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A thought experiment with Heisenberg's Uncertainty Principle [duplicate]
Possible Duplicate:
Could the Heisenberg Uncertainty Principle turn out to be false?
Thought Experiment
Ponder, for a moment, if I had a cube with 10cm sides which I'll name The Box. By ...
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The state of Indefinite metric in Quantum Electrodynamics
I faced difficulties to grasp why indefinite metric is introduced from no where in QED, after searching internet I found that this is a problem in QED, because one needs it to preserve theory's ...
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Is there Pair production in between charged plates
In classical electromagnetic theory, If parallel plates are charged oppositely and placed close to each other, there will be no charge will not flow from one plate to another.
How does this situation ...
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Is diffraction affected by interaction between photons and electrons?
Suppose we take a sheet of ordinary metal, make a narrow slit in it, and shine a light beam through the slit onto a screen. The light beam will diffract from the edges of the slit and spread out onto ...
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Nonlinear refraction index of vacuum above Schwinger limit
This question is more about trying to feel the waters in our current abilities to compute (or roughly estimate) the refraction index of vacuum, specifically when high numbers of electromagnetic quanta ...
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252 views
What is the 'quantum-developed' or 'relativistic-developed' equation of the electrostatic force?
Quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics that is the first theory where full agreement between quantum mechanics, special relativity and ...
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Why possibility for X-ray to excite inner electrons higher than outer electrons?
It seems X-ray absorption spectroscopy is usually ascribed to the interation between photons and inner electrons. Does it mean inner electrons are much preferred by X-ray photons to outer electrons? ...
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A step in the derivation of the magnetic momentum of the electron in Zee's QFT book
In chapter III.6 of his Quantum Field Theory in a Nutshell, A. Zee sets out
to derive the magnetic moment of an electron in quantum electrodynamics.
He starts by replacing in the Dirac equation the ...
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3answers
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If electromagnetic fields give charge to particles, do photons carry charge?
As I understand these two statements:
An electromagnetic field gives particles charge
A photon is a quantum of electromagnetic field
It must mean that a photon carries charge. But I guess it isn't ...
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794 views
How does charge work if photons are neutral?
How can an electron distinguish between another electron and a positron? They use photons as exchange particles and photons are neutral, so how does it know to repel or attract?
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QED: Would atoms without electrons be visible?
I have been reading a lot of QED books lately, and understand (as well as possible anyway) the interaction between electrons and photons. But I can't seem to get a clear indication of the interaction ...
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Is wave–particle duality considered a valid interpretation of the behavior of photons?
There are a number of questions on this site that explain the many wave-like behaviors of photons by making reference to wave-particle duality.
However, I have just finished reading Feynman's book ...
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Orbital momentum and spin transfer through gauge mediator
I study the jellium model: conduction electrons free except for their mutual repulsion. We have the following vertex:
...
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What is predicted to happen for electron beams in the Stern-Gerlach experiment?
The Stern–Gerlach experiment has been carried out for silver and hydrogen atoms, with the result that the beams are deflected discretely rather than continuously by an inhomogenous magnetic field. ...
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What is the massless limit of massive electromagnetism?
Consider electromagnetism, an abelian gauge theory, with a massive photon. Is the massless limit equal to electromagnetism? What does it happen at the quantum level with the extra degree of freedom? ...
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How many photons can an electron absorb and why?
How many photons can an electron absorb and why?
Can all fundamental particles that can absorb photons absorb the same amount of photons and why?
If we increase the velocity of a fundamental ...
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Stability of a rotating ring of multiple electrons at relativistic speeds
There was a time when physicists where concerned about electron internal structure. The rotating ring model was one of the proposals to explain how a charge density could become stable against ...
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2answers
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numerical formulation of Dirac equation plus electromagnetic field
I have the following equations describing the electron field in a (classic) electromagnetic field:
$$ c\left(\alpha _i\right.{\cdot (P - q(A + A_b) + \beta mc) \psi = E \psi } $$
where $A_b$ is ...
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Electromagnetic charge [duplicate]
Possible Duplicate:
If electromagnetic field give charge to particles, does photon carry charge?
Is it possible to charge photons
I was wondering if light when it's in wave form (seeing ...
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233 views
Why 2s state is lower in energy that 2p state in atoms?
The s orbital have higher probability to be closer to the core and feels larger attraction than the p orbital and on average is further away and in addition p has repulsive potentilal l(l+1)h^2/2mr^2. ...
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How Lyman transition (to the ground state from higher excited) happens ? The dipole selection rule is +/- 1?
How are the lyman series observed when the dipole selection rule is +/-1 in l change for hydrogen atom ?
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Is there any analogy between electron positron annihilation and brane anti-brane annihilation?
I would like to know if there is any similarity between electron positron annihilation and brane anti-brane annihilation? Is it there then can we use electron positron annihilation knowledge to study ...
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How did QED diverge from quantum mechanics mathematically?
We have either Heisenberg or Schrodinger picture of quantum mechanics world. So, how did quantum electrodynamics come from mathematical formulations of quantum mechanics?
Also, QED seems to have ...
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Is there a strong force analog to magnetic fields?
In special relativity, magnetism can be re-interpreted as an aspect of how electric charges interact when viewed from different inertial frames.
Color charge is more complex than electric charge, but ...
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Representation of phase in quantum mechanics
[Note: My discussion of the three answers can be found just after the question.]
Imagine three points in space that differ only by a phase angle of "something" (what doesn't really matter).
One way ...
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1answer
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What's the wavelength of an electron after hitting a potential barrier?
I have this question:
An electron with Energy $E = 40 eV$ hits a potential barrier with $E_0 = 30 eV$. What is the wavelength of the electron after hitting the potential barrier?
I worked from ...
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237 views
Does electric charge affect space time fabric?
I am confused with this question. Does electric charge affect the space time fabric? If so, why? Also if electric charge does not affect the space time fabric, how can we interpret the origin of the ...
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What tree-level Feynman diagrams are added to QED if magnetic monopoles exist?
Are the added diagrams the same as for the $e-\gamma$ interaction, but with "$e$" replaced by "monopole"? If so, is the force between two magnetic monopoles described by the same virtual ...
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If the electron is point like, then what is the significance of the classical radius of the electron?
What is the physical meaning/significance of the classical radius of the electron if we know from experiments that the electron is point like?
Is there similarly a classical radius of the photon? The ...
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1answer
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Optical waveguide that can displace a 4D light field
Has anyone invented an optical waveguide that can "pipe" a scene from one place to another unaltered? More precisely, I want to displace (and/or rotate) a 4D light field.
An optical waveguide is an ...
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What's the role of field equation in QFT?
For free field theory, it seems the solutions of a field equation are used to give a representation of Poincare group, and the field equation is still satisfied after quantization. However for an ...
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experiment proposal to validate microcausality
I've been wondering about microcausality for some time now (a recent question of mine regarding the topic) and i'm wondering if its possible to devise an experiment to detect potential violations
I ...
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After quantization of electron vibrations, do we need electrons anyway?
The title question is not ment in a general context, but one in which goes to the plasmon theory.
In that case, how is are the statistics (boson vs. fermions) of plasmons determined?
And is there an ...
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Is there a simple explanation for Schwinger's relation g=2+alpha/pi for the g-factor of the electron?
Schwinger has on his grave (it seems) the relation between the g-factor of the electron and the fine structure constant:
$g = 2 \ + \ \alpha / \pi \ + \ ... $
Did Schwinger or somebody else ever ...
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1answer
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Will an entangled idler electron induce a current in a conductor if the signal elctron's spin is measured?
I'm assuming a hypothetical setup as follows: Two labs (Alice and Bob) exist. Each has one electron of an entangled pair. At Alice, the electron travels through free space towards a magnetic field of ...
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Maxwell's equations in microscopic and macroscopic forms, and quantization
The macroscopic Maxwell's equations can be put in terms of differential forms as
$$\mathrm{d}\mathrm{F}=0,\quad\delta \mathrm{D}=j\implies \delta j=0,\quad \mathrm{D}=\mathrm{F}+\mathrm{P}.$$
...
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Does the wave nature of a particle refer to the wave function?
In quantum mechanics when we talk about the wave nature of particles are we referring in fact to the wave function? Does the wave function describes the probability of finding a particle (ex: ...
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Do composite particles that are electrically neutral but have charged constituents radiate?
For example an electron radiates when accelerated. So does a positron. But is the radiation emitted by accelerated positronium the sum of the radiation emitted by each separately? If not, why not? If ...
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Why isn't light scattered through transparency?
I'm asking a question that has bothered me for years and years. First of all, let me give some context. I'm a layman in physics (college educated, math major). I've read Feynman's QED cover to cover, ...
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Why/how does an electron emit a photon when decelerating?
I've had two special relativity courses so far but none really gave me a clear description of the process.
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Why did Feynman's thesis almost work?
A bit of background helps frame this question. The question itself is in the last sentence.
For his PhD thesis, Richard Feynman and his thesis adviser John Archibald Wheeler devised an astonishingly ...
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Radiative Corrections and Bremsstrahlung
I am having trouble understanding why it is consistent to include "Breamsstrahlung" diagrams in computations of scattering amplitudes.
For example, consider the scattering of two electrons to two ...
