All Questions
Tagged with quantum-electrodynamics electrons
118 questions
4
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1
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Are angular momentum selection rules only understood for hydrogen like species?
I am someone with a rudimentary understanding of atomic and molecular physics, and with that I'm trying to understand in which case which selection rule becomes applicable. For the angular momentum ...
- 111
1
vote
0
answers
53
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What is the status of Wheeler’s ‘one-electron universe’ idea? [duplicate]
I'd like to ask the experts about the following:
Sometime ago, I read about the One-electron universe postulate by Wheeler, and I found the concept fascinating. I wonder if it is a line of work that ...
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-3
votes
1
answer
87
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What is the maximum amount of energy one electron can have? [closed]
Is there any limit on the amount of energy one free electron can have?? Certainly there should be a limit. I think High Energy Physics should be able to answer it. Please somebody help.
- 11
0
votes
1
answer
56
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Wave-particle duality: interactions of like / different quantum fields
With my pop-sci level of understanding, it seems to me that quantum fields exhibit particle-like properties only when interacting with a different quantum field - i.e. electromagnetic field interacts ...
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2
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0
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55
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What is the proper ansatz for describing an electron-photon many-particle System?
I am somewhat used to simplified non-relativistic quantum mechanics (both canonically and grand canonically), describing a system by a Hamiltonian containing a kinetic part, an external potential as ...
- 1,280
6
votes
4
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167
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Does one electron in superposition repel itself?
Consider Quantum Electrodynamics, and consider the electron field to be in a state which is a superposition of two wavepackets, each located in a different spatial position. Explicitly:
$$|\psi\rangle ...
- 1,096
6
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2
answers
276
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Scalar QED atoms - will they pass through each other?
Atoms generally do not pass through each other. This is usually attributed to the Pauli exclusion principal between the electrons (see links below).
If the electrons and nucleons were switched with ...
- 2,200
3
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1
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329
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Are QED Feynman diagrams readable in any order?
I have somewhat of a basic question regarding QED Feynman diagrams. To expose my doubts let's take the Feynman diagram of the Compton scattering (at the second order) as an example:
With the solid ...
- 4,635
0
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1
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85
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Can there be an electron without photons?
Can the electron field be excited while the photon field is not? I'm guessing the answer is no, because electrons are supposed to interact with their own electric field. I don't know about ...
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0
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77
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Can the electron $g$-factor be understood as electrons having roughly twice as much momentum as the Bohr Magneton?
I'm trying to make sure I understand the $g$-factor of the electron, so if my question is flawed please don't just point out my flaws, but help me correct my understanding
If I understand correctly ...
2
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1
answer
46
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Spin magnetic dipole moment of electron not an invariant with acceleration?
Since the energy of the electron at rest can be calculated by:
$$
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 $...
- 4,376
0
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0
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62
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Feynman Chapter 13
I was reading Feynman's lectures on Quantum Mechanics. In chapter 13 he derived the amplitude to find an electron in a 1-D lattice for a stationary state. This amplitude is a pure immaginary number ...
-2
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1
answer
191
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Is the fine structure constant a function of electron mass? [closed]
The main statement is: the EM coupling constant is energy dependent, and the fine structure constant (FSS) is the low energy limit. This means that the flow of the coupling constant vanishes when the ...
- 1
1
vote
3
answers
144
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Do free electrons always interact with any photon they 'contact'?
Do free electrons (plenty of them in space and in stars) scatter every photon they come across?
Free electrons, unlike those in atoms and molecules, don't have specific energy levels after all...
Isn'...
- 4,709
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2
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137
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Is the spin magnetic dipole moment of the free electron not at rest the same as its rest value?
As far as I know all experiments measure the rest value of the spin magnetic dipole moment of a free electron indirectly (i.e. apparently there is yet no method or apparatus to directly measure this ...
- 4,376
1
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1
answer
146
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What would happen if a magnetic monopole collides with a magnetic antimonopole?
According to Dirac, theoretically, each Magnetic Monopole (North mm) is connected with their counter partner in space, the Magnetic Antimonopole (South mm) via an infinite thin and possible long ...
- 4,376
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0
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52
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Are photons the sources for the electron field?
I'm self-learning QFT, so please excuse my inaccuracies.
Consider the complete quantum electrodynamic action:
$$\int d^4x \bar{\psi}(i\gamma^\mu \partial _ \mu - m)\psi + A_\nu J^\nu - \frac{1}{4}F^{\...
- 1,376
-2
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1
answer
73
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Why the electron having a relative light mass $511keV$ is so small, upper limit $10^{-18}$m, in the SM? [duplicate]
Usually in particle physics larger mass refers to a smaller cross-section of a particle or atom thus a smaller sized particle.
How a so relative light mass particle only $511\,\mathrm{keV}$ can be so ...
- 4,376
0
votes
2
answers
202
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Why does the proton have the same elementary charge value $e$ as the electron? [duplicate]
Maybe a silly question but I am looking for an analytic explanation of it.
I think I already have one but I want to see if there is a better one, more fundamental?
What does it mean fundamentally ...
- 4,376
1
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5
answers
279
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Force between two protons
Yesterday my teacher was teaching about the production of photons, he told that photons are produced when the electron move from a higher energy level to a lower energy level then suddenly a idea ...
1
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0
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169
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Electron positron annihilation to more the 3 photons
I understood why a single photon can't be released from the annihilation of an electron and positron and that the common cases are 2 and 3 photons. I have two thing's I'm unsure of:
why is the ...
- 21
3
votes
3
answers
773
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Are there in nature any Right Chiral isolated electron particles?
Note: I refrain from using the concept of handedness and the terms left-handed and right-handed when referring to chirality since these usually refer to the helicity of charged fermions and their ...
- 4,376
1
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0
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234
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Drawing Feynman diagram for positronium decay into 2 photons
I am studying the annihilation processes and read that electron-positron annihilation releases 2 photons. I know that releasing 1 photon is not possible because it violates the conservation of $E$. ...
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1
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1
answer
68
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QFT for an extended electron
Has somebody already formulated a QFT (e.g. QED) for an extended electron (e.g. as a spherical charge) such that the point particle limit gives the usual QFT?
Is anything know about the connection of ...
- 498
1
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2
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93
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Simple Quantum Electrodynamics question
First of all, what causes electrons to emit photons in QED? Why wouldn't electrons just not interact in that way
Second question, how do electrons even get close enough to interact/exchange photons. ...
- 21
1
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1
answer
71
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Visibility and virtual photon?
Photons could be perceived as light as they could excite electrons in the photoreceptors of the eye as photons are the EM force carriers.
For transmitting electric forces of a stationary electron, the ...
- 11
1
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0
answers
63
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What is the Hamiltonian of an electron moving through a conductor?
I am specifically asking for the formula for an electron moving through a wire. I would also like to know where it comes from/how it is derived. I was not able to find any answers for the potential ...
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11
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1
answer
605
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Why an electron and a positron should have the same lifespan?
According to Particle Data Group:
source: data
Particles and their antiparticles (i.e. antimatter) have the same lifespan.
The electron/positron for example have a minimum of 6.6E28 yr. This was ...
- 4,376
0
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2
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126
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How close together can an antiparallel magnetic moments free electron pair get? [closed]
See illustration below:
Is there a calculation-prediction of the minimum distance separation of an antiparallel electron pair due its like charge repulsion?
There must be an equilibrium between the ...
- 4,376
4
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1
answer
102
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Induced current in vacuum
We all know that an electron will induce vacuum polarization. But what if I have a current in a wire? Will this current induce another current in vacuum? Or something like a virtual current?
In other ...
0
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1
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139
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How the magnetic moment of subatomic particles is a prediction of QED?
What I read on Wikipedia is
… quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory ...
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0
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1
answer
63
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Can one-electron world theory be revived if the Sakharov's conditions are completely met?
Regarding that people object about the matter antimatter balance in the one-electron world theory to discard it, can it be once more revived if the Sakharov's conditions are met so that the matter ...
- 1,280
1
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1
answer
143
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Is there a chance (in QED) that two electrons move from two spacetime points to two other points without interacting?
Is there a "zeroth-order" effect in quantum field theory (QED) that two electrons move from two fixed spacetime points to two other fixed spacetime points without the presence of virtual ...
1
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0
answers
60
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If the Landé $g$-factor of an electron is its magnetic moment due to its inherent quantum spin, and its spin is its magnetic moment, why isn't it 1? [duplicate]
I was taught that the 'spin' of an elementary particle was its inherent, unalterable magnetic moment due to its physical spin, or angular momentum, that may or may not actually exist.
Therefore, if ...
- 4,709
0
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1
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159
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What are the operators associated to the electron/electromagnetic quantum field?
After reading through a number of questions on SE including What are field quanta? and What are quantum fields mathematically?, I am still struggling with what specific operators are associated to ...
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1
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142
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What happens to an electron when it radiates a photon?
I recently came across this Feynman diagram:
For a more simplistic diagram, I suppose even this would be adequate:
As you can see in these diagrams, they radiate these virtual photons. The virtual ...
- 136
2
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1
answer
473
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What will happen to you if I hit you with an electron after accelerating it to the maximum speed possible?
Electrons have very small mass and they are charged particles so they can be accelerated using strong electric fields. Also the mass of the electrons' mass will change significantly if it is ...
user276626
13
votes
3
answers
1k
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What makes the electron, as an excitation in a field, discrete?
In standard quantum mechanics, the wave function have discrete energy-values due to a potential. However, my very limited understanding of QFT is that electrons are excitation in the Dirac field, and ...
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3
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687
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Do virtual electron-positron pairs have mass?
When a photon produces an electron-positron pair, do both these particles have mass? Why or why not?
- 369
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1
answer
71
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Kallen-Lehman and one particle state of electron for QED
We did the Kallen-Lehman procedure in lectures for phi to the fourth theory. We also defined the wavefunction renormalisation. At the end our lecturer briefly mentioned that to carry it over to QED ...
- 420
2
votes
1
answer
453
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Why does the chances of particular Feynman diagram occurring reduces by 1% at each photon-electron interaction?
I saw a youtube video regarding Quantum Electrodynamics which explained how one can eliminate the Feynman diagrams with complex photon-electron interactions or loops. The guy explained that each time ...
- 1,378
3
votes
1
answer
45
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Elementary neutral fermions cannot be deflected in an inhomogeneous magnetic field?
Can we say that elementary neutral fermions cannot be deflected in an inhomogeneous magnetic field? In other words, is it true that if a neutral particle is deflected by an inhomogeneous magnetic ...
- 12.3k
1
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2
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151
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Does the probability that an electron absorbs a photon change with the distance between the two?
Suppose there is an electron and a photon. For simplicity, no other forces are influencing the particles. Does the probability that the electron absorbs a photon change if the photon moves to a ...
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1
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197
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In QED why is the electron a point particle? [duplicate]
I read Feynman's book but this still unclear to me.
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1
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0
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174
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Is the cut-off energy in the calculation of the electron's self-energy associated with an electron size?
I have got two questions on the self energy/point particle concept of the electron:
What do physicists exactly mean when they say the elementary particles (e.g. the electron) are point particles?
...
- 498
0
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0
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70
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Electric field outside a standing electron wave
If an electron were confined in a cavity with perfectly reflecting ends, its wave function would form a standing wave in the cavity. Presumably the electron would not emit EM radiation unless it were ...
- 25k
0
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0
answers
264
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Feynman self-energy diagrams
In the Feynman picture, I don't understand how virtual photons in the self-energy diagram for a rest-frame electron can have energies that exceed $2m_e$. Aren't negative energy states of the electron ...
- 1
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0
answers
40
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Why are 2 gamma photons created? [duplicate]
When a positron and an electron come together they annihilate and produce 2 gamma photons
$$e^+ +e^- \rightarrow 2\gamma$$
I can understand that they must be produced in pairs to conserve momentum. ...
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46
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5
answers
7k
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Do electrons really perform instantaneous quantum leaps?
This is not a duplicate, non of the answers gives a clear answer and most of the answers contradict.
There are so many questions about this and so many answers, but none of them says clearly if the ...
- 29.3k
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1
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The electric and magnetic field, reaching to infinity
I have difficulty’s to accept that the electric and magnetic field components of photons as well as of electrons and the other subatomic particles are extended to infinity. For practical use that does ...
- 10.8k