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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Which of the following produces more current? [closed]

In (1) photoelectric effect, (2) Compton effect, and (3) pair production, a beam of electrons are released. Out of Three Which produces More current? And How?
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Positronium energy level in QED

I'd like to know if it is possible to compute positronium mass and lifetime from a QED approach. I'm searching for some literature on how to treat resonances in QED (or general QFT) ; most of the ...
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Energy conservation if photon absorbed below resonance

Suppose I have some quantum system (like atom) with excitation energy $E_{exc}$ which is homogeneously broadened due to finite lifetime. I shine light with narrow spectrum centred around energy ...
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Tape as a X-Ray Source

A couple years ago I ran upon a YouTube video demonstrating how researchers used x-rays given off by tearing tape off its spindle in hopes to miniaturized and cheapen future x-ray devices. As of ...
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Charge dependence of operators in QED renormalization

Consider a UV cutoff regulator $\Lambda$ with an effective QED lagrangian: $\mathcal{L}_{\Lambda} = \bar{\psi}_{\Lambda}(i\not \partial - m_{\Lambda})\psi_{\Lambda} - ...
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Electric field due to rotating charged sphere

Consider a spherically symmetric charged object (charge $Q$) rotating about its axis. From Gauss's law we know that all that matters for the electric field $\mathbf{E}$ is the charge $Q$ enclosed ...
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Differential cross section for photon scattering on fixed magnetic dipole

Photon with energy $\hbar\omega$ scattering on a fixed particle with magnetic momentum $\vec{\mu} = \mu \vec s$. How to calculate a differential and total cross section for the photon. I've found in ...
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Can a quark irreversibly pass though an event horizon?

This is an attempt to transform a question I asked about a year ago into a binary yes-or-no question: Since a quark has electrical charge, can it irreversibly pass though an event horizon? The ...
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108 views

One loop correction to $F^2$ in massless QED, question from Peskin & Schroeder

In Peskin & Schroeder chapter 19, about trace anomaly in massless QED, the trace of $\Theta^{\mu\nu}$ is given by $$ {\Theta^\mu} _\mu =-\frac{4-d}{4} (F_{\lambda\sigma})^2 + (1-d) \bar{\psi} i ...
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Regularization of infrared divergences

Let's have diagrams in QED when we don't use Feynman gauge. Then the bare photon propagator will look like $$ \tag 1 D_{\mu \nu}(p) = -\frac{g_{\mu \nu} - \frac{p_{\mu}p_{\nu}}{p^{2}}}{p^{2} + ...
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239 views

Can the diffraction/interference pattern behind the slit (double slit) be calculated with Feynman path integrals (QED)?

I often see Feynman path integrals explained by a graphic which shows the slit and then the electron goes all possible ways behind the slit. Ok that is nice to understand the Feynman path integral, ...
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Wave-like description of Compton scattering and photoelectric effect

I have found in the wikipedia page for QFT the following statement: ... Although the photoelectric effect and Compton scattering strongly suggest the existence of the photon, it is now understood ...
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Connection between Gauge Fixing Term and Gauge Condition [duplicate]

In Peskin on page 514, when deriving the Faddeev-Poppov ghosts, they arrive at the full Lagrangian for Yang-Mills: $$ \mathcal{L} = -\frac{1}{4}F^2 + \frac{1}{2\xi} (\partial \cdot ...
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Why is the Higgs mass renormalization considered a fine-tuning problem, while the electron mass (in QED) isn't?

Don't both masses require infinite corrections in their renormalization procedure? It is my understanding that the electron self-energy in QED increases to infinity with increasing cutoff value on ...
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139 views

How does exciting an electron's surrounding electromagnetic field cause 'electron excitation'?

In more meaningful words than the ones above, how does adding energy to the EM field cause the electron to to change orbitals or oscillate in a different pattern.
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Do plasmons depend on the ambient EM field?

Imagine a situation: There's an illuminated metal slab in vacuum. Normally, there are some plasmons created running all over the slab. What would happen if we had turned a giant magnet near the slab? ...
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Quantum fluctuations in the non-relativistic limit

Is there any way to describe quantum fluctuations in ordinary quantum mechanics? For instance, a proton fluctuating into a proton-$\pi^0$ state and then back to a proton? What are the relevant ...
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Can or does the Casimir effect play a role in solving the electron self-energy problem?

The Casimir effect is usually derived for parallel plates, with the pressure going as the inverse fourth power of the separation. It strikes me that this implies that a tiny spherical shell of charge ...
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Hamiltonian formalism in quantum electrodynamics

I need to compute $\frac{d}{dt}\hat{\mathbf P} = \frac{d}{dt}(\hat{\mathbf p} - q\hat{\mathbf A})$ for the solutions of $$ (i\gamma^{\mu}\partial_{\mu} + q\gamma^{\mu}A_{\mu} - m)\Psi = 0. $$ May I ...
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spread of fock state distribution and infinite revival time of rabi oscillation in spontaneous emission

In cavity QED for a 2-level atom, the revival time for oscillation b/w the states $\left|\ e\ 0\right\rangle$ and $\left|\ g\ 1\right\rangle$ (absorbing the same photon that is emitted) is said to be ...
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EMF induced in a dynamo is by photons of permanent magnets?

i know little about the quantum field theory and also that the permanent magnets have there fields because of exchange of virtual photons across or around the ends. so when we take a dynamo and the ...
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How does QED deal with wavelength of quanta [duplicate]

Since QED treats photons as individual units (quanta) how does it treat the concept of the "wavelength" associated with the photon?
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Photons interact with themselves

We know that photons are the antiparticles of themselves and if they interact with each other through higher order process do they annihilate and again produce photons? Here is the Phys.SE question ...
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Relationship between classical electromagnetic wave frequency and quantum wave function + de broglie frequency

As it is. As I study through classical mechanics and quantum mechanics, I began to wonder whether there is a relationship between classical electromagnetic wave frequency and quantum wave function ...
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Can we use only the observables of Fermion fields?

There are legion ways to consider fermionic Dirac spinor fields, but is it possible to consider the asymptotic free field only in terms of observables, which in the case of the Dirac spinor field must ...
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Are virtual photons affected by effective gravity in non-linear quantum electrodynamics?

Quantum electrodynamics based upon Euler-Heisenberg or Born-Infeld Lagrangians predict photons to move according to an effective metric, which is dependent on the background electromagnetic field in a ...
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Could gravity hold electron charge together?

Could the gravitational force be what holds the charge of the electron together? It seems to be the only obvious possibility; what other ideas have been proposed besides side-stepping the issue and ...
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Relating Quantum Mechanics to Classic Electromagnetism [duplicate]

I've been directed to a few articles, and I am sure there is a related post, but can someone explain the procedure by which we can view classic electromagnetism through quantum mechanics? Indeed we ...
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Would the detection of advanced waves be possible in curved space-time?

In the transactional interpretation of quantum mechanics reference 1, inspired by the Wheeler–Feynman absorber theory, a transaction is formed between the emitter and absorber by a superposition of ...
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Can QED explain this or do I have revert to the classical model of light?

I want to know can QED can explain this image,like why there are someplaces with low light (shadows) like behind the chair, and why there are some places that are bright(rest of the floor). I know ...
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Can we find the definite path of electron?

Light can crisscross in all directions. Source: Can photons pass through each other? In a given volume, we can have light throughout, such that there is no space with no light in it (with the ...
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What happens to theoretical physics if a photon has non-zero mass?

I want to know the theoretical implication if photons have a non-zero mass. What happens to the Maxwell equations? What happens to QFT? If the photon have mass it can decade?
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Why is electric charge conserved?

We have long been taught that electric charges are neither created nor destroyed. But somehow it is okay to destroy two oppositely charged particles at once ! Why is that so? Let's just take a look ...
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Can a photon survive a collision? If so, is it at rest during the process?

Background Irving Kaplan, in Article 6.7: The Compton Effect of Nuclear Physics (2nd Ed.) explains the Compton effect as follows: Compton (1923) was able to show that when a beam of ...
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Why does Quantum Electrodynamics Allow a Photon to Exist Temporarily as a Positron and an Electron?

In this question... Why does a photon colliding with an atomic nucleus cause pair production? ...I asked why a photon colliding with a atomic nucleus can become an electron and a positron. The ...
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What actually happens when light meets a surface(QED or QM or Condensed matter physics)?

I want to know what actually happens when light meets a surface like water or wood. Quantum mechanics says that objects are neither "transparent" nor "opaque". Rather a system as a whole can accept ...
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Why quantum electrodynamics? [duplicate]

Most of the people seem pretty much content with classical electromagnetic theory .And most of the applications use classical EM theory .However, in such situations I would like to know what was the ...
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Why doesn't a changed particle ever lose energy by interacting with others by radiation of virtual photons? Are all virtual photons exchanged?

I've had it explained to me in a separate post that charged particles are constantly exchanging virtual particles with other charged particles and their energy is a steady state. How it is a surety ...
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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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Conservation of energy and momentum in photoelectric effect

Sometimes it is shown that in a Compton scattering it is not possible that the photon transfers all it's momentum and energy to the electron, see for example here: If one assumes complete energy and ...
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Is the glass made up of holes that let the light to go through it?

The following passage has been extracted from the book "The Magic of Science-A.Frederick Collins" (1917): Substances of all kinds have pores or holes in them. A sponge has pores that can be ...
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Inductor's energy

I have some knowledge about LC circuits, like I know Maxwell's equations, the differential equations of circuit oscillator and so on. I am armed with equations to solve physical problems involving ...
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Covariance of the Dirac equation and Infinitesimal Lorentz transformation

Okay, I've got really desperate now. I've spend 10 hours of work (for a few days) trying to prove 'trivial' equation in Quantum Electrodynamics. To anybody who want to write an answer for my questions ...
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Conservation of electric charge in Feynman diagram

Here is a Feynman diagram showing the mutual annihilation of a bound state electron positron pair into two photons: Is the electric charge conserved at the point A (or B)? What is the "charge" of ...
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Spin of an electron [closed]

I have a conceptual difficulty in understanding the electron spin. On the one hand, it is an experimental, observable feature of electrons. The problem is in understanding to what it belongs - to a ...
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406 views

What is the spectral energy density of virtual photons around a unit charge at rest?

Given that my previous question, namely "What is the number density of virtual photons around a unit charge?" has no precise answer, here is a more precise wording: What is the virtual photon ...
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101 views

$U(1)$ local gauge invariance in QED [duplicate]

While constructing Lagrangian of QED, we don't add the mass term for photon $\dfrac{1}{2} m^{2}A_{\mu}A^{\mu}$ because gauge invariance does not allow. I want to ask, whether "$\bf{Theoretically}$", ...
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Is it possible to give photons an electric charge? [duplicate]

I know that photons have no electric charge and that they are stable, but is it possible to give them a positive or negative charge? If so how?
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Is colour a purely quantum effect?

If the colour of an object is determined by the wave-lengths of light that is absorbs and reflects (?) then can colour be described as a purely quantum effect (i.e. without quantum effects an objects ...
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