All Questions
236,734
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What is the electric field strength of a photon? In V/m or N/C? Or its magnetic field in Gauss or Tesla? For visible light, or gamma rays?
I am thinking of this now because I have been learning about the Schwinger limit (or Schwinger effect)...
Supposedly, a strong-enough electric and/or magnetic field creates a 'nonlinear' effect in the ...
- 4,509
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Saddle Shaped Universe
The universe, as described by FLRW metric, if $k = -1$ is clearly a 2 sheet 3-hyperboloid described by $x^2+y^2+z^2-w^2=-R^2$. So where does the more common saddle shaped picture of the open universe ...
- 1,121
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How to find Casimir operator eigenvalues of SU(N)
The [f1, f2, f3…fn] in the image represent the irreducible representations of SU[n]. How to find the irreducible representations of SU[n] that conform to the form [f1, f2...fn]. Can you give me the ...
- 11
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What are the operators here and how are these formulas derived? [closed]
In (23), are grad and div some kind of scalar operators comparing to $\nabla$ and $\nabla\times$? because tbh I dont know how $\text{curl}(\mu^{-1}\text{curl}\textbf{A})$ turns into $\text{div}\mu^{-1}...
- 103
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Weisskopf and self-energy
I am working my way through the 1934 paper by Weisskopf on the self-energy of the electron and is much helped by the English translation found here. Below is a screenshot of two pages. I can very ...
- 61
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34
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Visualization of resistance
What does a resistor do in an electrical circuit? Does it impede the flow of electrons by increasing offering a path that offers a large no. of collisions? How can i visualise it, i have been told to ...
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-4
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Standard Model Generational Disparity
This may appear to be opinion based at first glance, but I believe it has conceptual merit.
The Standard Model contains 3 generations of particles: $e~–\mu~–\tau$, Up–Charm-Top, etc. But the 2nd and ...
- 9,333
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3
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19
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Comparing Electric Potential Energy of two Charges
I do not know what I am missing here and would appreciate a little help in figuring out the flaw in my logic. I have a row of positive charges and a row of negative charges as shown in the image above....
- 1
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Calculating the amount of torque applied to to stop a rod rotating at some angular velocity
Consider a Rod AB, having length $l$ with non uniform mass density $\lambda (x) $ a function of length from the end A, is rotating at an angular velocity $\omega$ with fixed end A and free end B. ...
- 169
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Path integral without wick rotation [closed]
As far as i know path integrals are usually evaluated by wick rotation to imaginary time, then making imaginary time finite and periodic/anti-periodic (bosons/fermions) with period beta=1/T (inverse ...
- 367
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27
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Voltage: work to move a charge, or difference of electric potential?
Let's say I have a single positive charge inside of an electrostatic field. I want to move this charge from point A to point B and determine the voltage between the two points.
Points A and B are the ...
- 3
2
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1
answer
39
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Do thermodynamic cycles occur only in human-made machines?
Intuitively, it seems like heat engines and refrigerators require a good bit of technology to make a working substance pass through different thermodynamic states and then finally return to the ...
- 173
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21
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Is there a superfluid dual to superinsulators?
It's well known that there are many analogies between Superconductors and Superfluids. The diagram below explains a few:
$$ \begin{matrix} \bf{\text{Superconductors}} \\ \text{0 electrical resistance} ...
- 2,969
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2
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Do objects really "fall" at the same rate? [duplicate]
I understand that a hammer and a feather were dropped on the moon and they both landed at the same time. I understand that for all practical intents and purposes all objects do fall at the same rate.
...
- 131
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What is the impressed current density?
I don't have a too solid background for physics and am reading some engineering books of electromagnetics. What is the impressed current density here? I think it is Ohm's law but couldn't find its ...
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