# All Questions

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### Concerning topology of BPS states of the M5-brane

My question is about the M5-brane in M-theory. I would like to know whether the BPS states of the M5-brane worldvolume theory (especially the 1/2 BPS and 1/4 BPS ones) are independent of the topology ...
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### Does Saturation velocity in semiconductors have a relation with the wavelength in which the peak in the absorption spectrum occurs?

Saturation velocity is the maximum velocity a charge carrier in a semiconductor, generally an electron, attains in the presence of very high electric fields. (source) I want to know if the ...
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I'm studying Classical Mechanics and there is one object that appeared recently on the book I'm not being able to get a physical intuition about it. The mathematical definition goes as follows: Let ...
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### Need help on understanding mechanical wave function

My textbook states that, equation 1 : y(x=0,t) = Acos($\omega$t) = Acos(2$\pi$ft), which I understand. However the book goes deeper stating also that, t-$\frac{x}{v}$, and $\frac{v}{x}$-t I am ...
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### What is meant by the expression “Markovian dynamics”

I know what a Markov chain is but what does it mean in physics when I say that I assume Markovian dynamics? For example in Quantum Mechanics, I read that it means that the time evolution can be ...
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### Jet turbine blades from single crystals, how are they formed?

I know about nothing about crystals, although I do know a bit more about jet turbine engines, and I definitely know that you don't want the fan blade hitting the fan housing. The reason given in the ...
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### Why do you lose hearing when you yawn?

When I yawn a great big yawn( it doesn't happen with "smaller" yawns), my hearing becomes harder, or goes away altogether, until I stop. Why does this happen? Because I can hear fine when I just open ...
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### The James Webb Telescope, why are there 5 levels of protecting foil?

From simple curiosity, does anybody know why there are around 5 layers of solar radiation reflecting foil on the James Webb Telescope, rather than one or two? Is it to save weight, or (probably) ...
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### Position from a Velocity-Time graph

Find the position at t= 3.0 seconds. The initial position is 2.3 m. I found the average velocity to be 3.33 repeating so I multiplied that by the time (3) to get 10 and then added the initial ...
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### Galaxy Cluster Data

I have a modification to MOND that appears to work much better than 'Standard' MOND at the galactic scale. I want to test this model now on larger structures. Does anyone know where I can find ...
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### Ball Rolling Down An Inclined Plane - Where does the torque come from?

There is a ball rolling down an incline, with no slipping. If we consider the point of contact between the ball and the inclined plane to be the pivot point (for our torque calculations), then I have ...
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### Why, fundamentally, are particles charged?

This is something that has long bothered me, and I have asked a few physicists and chemists and never gotten a very satisfying answer. Why are particles charged? And I'm not asking (and this is the ...
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### Dark Energy and Wormhole stability

Is it possible that the "negative energy" needed to create stable wormholes as theorized by Morris and Thorne (?) could be dark energy? Could this be the "exotic" negative energy matter referred to?
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### If spacetime is folded upon itself

Say there are two black holes about a parsec apart. You theoretically fold spacetime upon itself so that the singularities of the black holes are "touching". ...
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### Measurement of the energy of an atom using a cold substance

An atom was prepared in a superposition of ground state and excited states.I propose to measure the state by coupling the system to a cold enough substance. By cold enough I mean $$kT\ll E_1,$$ where ...
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### Examples of measure zero sets in physics

The problem with Riemann integration of functions like ${\chi }_{ℚ}(x)$ (a function which takes the value of 1 if $x\in ℚ$, and 0 otherwise) is usually used to show the need for defining the Lebesgue ...
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### What is a good introductory book on quantum mechanics?

I'm really interested in quantum theory and would like to learn all that I can about it. I've followed a few tutorials and read a few books but none satisfied me completely. I'm looking for ...
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### Opposing EMF's, in an odd arrangement…?

A conductor in case 1 has two separate uniform magnetic fields $B_1$ & $B_2$: The magnetic fields(the blue rectangles are the field regions parallel to the conductor, while X's are the field ...
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### Is the universe a Turing machine?

Reading about Computable numbers I wondered if there is any physical experiment that returns non-computable numbers or if there is any physical theory that needs non-computable numbers. Because if ...
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### Significance of higher harmonics

I am analyzing a noise signal and have identified the fundamental frequency of a tone and it's higher harmonics. Say for example given the signal below, The fundamental frequency has a sound ...
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### Relation between Clifford Algebra and Spinors? [closed]

As short as can be stated, I was wondering what is the exact relation between Clifford Algebra and Spinors? The closest I could get was via Wikipedia: "Spinors are typically defined as elements ...
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### Pulley and block velocity problem [closed]

Block B is moving towards right with velocity 'V'. What is the velocity of block A with respect to block B? Note that the string has negligible mass and is inextensible, also that the pulley has ...