Tagged Questions
2
votes
1answer
52 views
Given expectation values for E and B, can you find an associated state?
When we quantize the electromagnetic field, we develop the concept of the field operator $A(\vec{r},t)$ and the simultaneous eigenstates of momentum and the free field Hamiltonian (i.e., each ...
1
vote
1answer
87 views
Quantum Mechanics of Lenz's Law?
I've searched the internet and two famous QM books (Sakurai and Messiah) for Lenz's Law, but haven't found anything. So my question is what the quantum mechanical explanation to Lenz's law is? Can ...
4
votes
0answers
76 views
Is the search for a Simple-group-based Electro-Weak theory over?
Just wondering:
We know that, in its current form of the $SU(2)_L\times U(1)$, the electroweak theroy rides a wave of huge success. However, is it not possible that the correct simple group ...
3
votes
4answers
300 views
Collision of two photons
Could someone explain me how will be look like collision of two photons? Will they behave like:
Electromagnetic waves, they will interpher with each other and keep they wave nature
Particles and ...
1
vote
1answer
124 views
A classically trivial quantum field theory of electromagnetism
Presumably there is a field theory of electromagnetism that classically gives trivial equations of motion, but when quantized shows interesting topological phenomena. I am talking about the Lagrangian ...
0
votes
2answers
95 views
Field energy of/from virtual Photons
I have a slightly out-of line question:
Consider a single electron (or it's current if you please)
The EM field surrounding it will (no doubt) have an EM field energy (T) to go with.
The standard ...
4
votes
2answers
168 views
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? ...
4
votes
2answers
365 views
Aharonov-Bohm Effect and Flux Quantization in superconductors
Why is the magnetic flux not quantized in a standard Aharonov-Bohm (infinite) solenoid setup, whereas in a superconductor setting, flux is quantized?
0
votes
0answers
95 views
What would the universe be like if Electroweak symmetry were unbroken? [duplicate]
Possible Duplicate:
What happens to matter in a standard model with zero Higgs VEV?
What if the Higgs did not have a "Mexican hat" potential and the therefore it's vacuum expectation value ...
4
votes
0answers
130 views
Semiclassical QED and long-range interaction
I'm interested in the (very) low energy limit of quantum electrodynamics. I've seen that taking this limit does not yield Maxwell equations, but a quantum corrected non-linear version of them.
If ...
2
votes
3answers
312 views
Gauge invariance and form of the vacuum polarization tensor
In quantum field theory or condensed matter physics, the fermionic one-loop diagram gives rise to the polarization tensor
$$ Π^{µν} = Tr[ γ^µ G γ^ν G ] $$
If we couple the electrons to an ...
1
vote
2answers
140 views
How important are electromagnetic tidal effects in QFT? Can they be used to determine whether a particle is point-like?
I just did a back-of-the-envelope calculation, which surprised me. I calculated the difference in acceleration (due to repelling like-charges) experienced by two sides of an electron the size of the ...
1
vote
1answer
284 views
Is there orbital angular momentum for all particles?
Light as an electromagnetic wave can be polarized in different ways, e.g. linear or circular. As far as I understand it currently this can be compared to the spin direction of a propagation electron ...
3
votes
1answer
305 views
Higgs Field compared to EM field
So, I've been reading about the Higgs because of all of this excitement lately with the LHC. I'm just a layman in physics but one thing I understood was that the Higgs field permeates all of space ...
2
votes
0answers
267 views
Gauge invariance and Feynman path-integrals
Let me look at the Hamiltonian of a charged particle in a plane in a constant magnetic field ($\vec{B}$) pointing upwards - then in usual notation it is,
$$\hat{H} = \frac{1}{2m}\biggl(\hat{p} + ...
4
votes
2answers
596 views
What's the relation between virtual photons and electromagnetic potentials?
Given that:
1) virtual photons mediate the electric and magnetic force fields
2) the magnetic field is the curl of the magnetic vector potential
3) the electric field is the negative gradient of ...
4
votes
2answers
642 views
To what extent is the “minimal substitution” or “minimal coupling” for the EM vector potential valid?
In all text books (and papers for that matter) about QFT and the classical limit of relativistic equations, one comes across the "minimal substitution" to introduce the magnetic potential into the ...
1
vote
1answer
317 views
How is the operation of a Goldleaf Electroscope explained in terms of virtual particles?
If an electroscope is charged negatively the electrons on the leaves will repell each other and stand apart. It is clear than there is a steady force between the leaves that counters gravity. How is ...
9
votes
2answers
350 views
Essential background for QFT study
The preface to Mark Srednicki's "Quantum Field Theory" says that to be prepared for the book, one must recognize and understand the following equations:
$$\frac{d\sigma}{d\Omega} = ...
8
votes
2answers
321 views
Quantizing EM field
Why when we quantize EM field, whe quantize the vector potential $A^\mu$ obtaining vectorial particles (photons) like the elastic field (phonons) and we can't quantize directly the EM-field tensor ...
5
votes
0answers
194 views
1-form formulation of quantized electromagnetism
In a perpetual round of reformulations, I've put quantized electromagnetism into a 1-form notation. I'm looking for references that do anything similar, both to avoid reinventing the wheel and perhaps ...
3
votes
3answers
320 views
What is the density of virtual photons around a unit charge?
It seems that virtual photons also exist in vacuum. So the precise question is:
What is the additional virtual photon density due to the electric field of a unit charge?
Or: How many virtual photons ...
4
votes
4answers
311 views
What is the medium that allows magnetic fields *or any forcefield* to exist?
Magnetic fields are obvious distortions.. of.. something, but what exactly are they distortions of? Massive objects produce curvatures/gradients in space-time resulting in what we observe as ...
7
votes
3answers
1k views
Are Classical Field Theory and Quantum Mechanics of a single particle (nonrelativistic or “classical”) limits of Quantum Field Theory?
Recently I talked about QFT with another physicist and mentioned that the Quantum Field Theory of a fermion is a quantisation of its one-particle quantum mechanical theory. He denied this and ...
5
votes
2answers
313 views
What would the electromagnetic field of a massless electron look like
The Standard Model gives non-zero mass to the electron via the coupling to the Higgs field. Issues of renormalizability aside, this is fundamentally unrelated to the fact that the electron couples to ...
3
votes
2answers
795 views
What does an atom radiate: a wave packet or a single photon?
What does an atom radiate: a wave packet or a single photon?
5
votes
6answers
526 views
Interaction ranges in the Standard Model - Electrodynamics vs QCD
as you might know, the Standard Model of physics can be seen as a $U(1)\times SU(2)\times SU(3)$ gauge theory where each symmetry group accounts for different force fields.
The behaviour for the ...
10
votes
8answers
2k views
Is it possible to separate the poles of a magnet?
It might seem common sense that when we split a magnet we get 2 magnets with their own N-S poles. But somehow, I find it hard to accept this fact.(Which I now know is stated by Gauss's Law)
I have ...
5
votes
2answers
318 views
Notation for Sections of Vector Bundles
(Reformulation of part 1 of Electromagnetic Field as a Connection in a Vector Bundle)
I am looking for a good notation for sections of vector bundles that is both invariant and references bundle ...
8
votes
3answers
1k views
Electromagnetic Field as a Connection in a Vector Bundle
I would like to know more about Ehresmann connections in vector bundles and how they relate to the electromagnetic field and the electron in quantum mechanics.
Background: The Schrödinger equation ...
12
votes
7answers
2k views
What equation describes the wavefunction of a single photon?
The Schrödinger equation describes the quantum mechanics of a single massive non-relativistic particle. The Dirac equation governs a single massive relativistic spin-½ particle. The photon is a ...
