# All Questions

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### Can speed be entangled?

When reading about quantum entanglement, I see that all variables that are discussed (spin for instance) have discrete states. Can a continuous variable such as speed be entangled? In the case of ...
• 455
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### Relation between the Bogoliubov approximation and Hartree-Fock ansatz

Sometimes I work in the mathematical surrounding of the Gross-Pitaevskii equation (GPE) and I'm asking myself how different derivations of the GPE are related. Originally the GPE was discovered by ...
• 233
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### Distribution of collision point position of an ideal gas particle

Assuming a system consists of N identical particles in gas phase and very dilute. Particles are assumed to be hard-sphere with elastic collision. At instance only the particles with a speed of μ is ...
15 views

### Can someone explain the Bell's Theorem concept in a way that makes sense?

I have seen various explanations including some here, and so far they have not made sense to me. I will describe what I got from them. A good answer does not depend on reading how I misunderstood it, ...
• 2,421
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### Potential energy in a magnetic field + Lagrangian

Just like a charge has some sort of potential energy in an electric field, I'm sure it does in a magnetic field to, since both fields are essentially the same thing from different points of view. How ...
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### Looking for a mathematical model that explains the increase of heat intensity while time is going on

Consider we are overloading a CPI device with many tasks. It is obvious that the CPU temperature goes up when the time is increasing. Is there anyone who can help with modeling this phenomenon?
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### How to take the derivative of an eigenvalue equation in quantum mechanics?

Equation 2.1 is $$H_0(t)\vert n \rangle = E_n\vert n \rangle$$ Equation 2.8 is $$\langle m \vert \partial_tn \rangle = \frac{\langle m \vert \partial_tH_0 \vert n \rangle}{E_n-E_m}$$ In the following ...
11 views

### Converting air pressure to depth in water

So I am trying to measure water depth using the air line method. The water level can vary. An open ended tube is submerged in water and then filled with compressed air to purge all water that entered ...
4 views

### Band theory of Photonic crystals

I have a basic question about the band structure of photonic crystals. If I have a periodic potential, then Bloch-theory tells me that the bands yield the energy spectrum of the Hamilonian which is ...
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### Confusion in lenzs law and Electro magnetic induction

Lets say we have a loop of wire placed in xy plane, in empty space. Now if its kept in changing magnetic field growing in z direction so from lenz's law the loop tries to create an opposing field due ...
6 views

### Why does a moving charged body with acceleration produce electromagnetic waves and How? [duplicate]

Why does a moving charged body with acceleration produce electromagnetic waves and a moving charged body with out acceleration does not and it produces electricity? Why does acceleration in a body ...
1 vote
19 views

### Finding common eigenvectors for two commuting hermitian matrices

Let $A = \begin{bmatrix} 1 &0 &0 \\ 0& 0& 0\\ 0&0 &1 \end{bmatrix}$ and $B = \begin{bmatrix} 0 &0 &1 \\ 0& 1& 0\\ 1&0 &0 \end{bmatrix}$ ...
14 views

### Due to time dilation and space contraction, what would happen if we were massless and able to be take a ride on a photon what would we experience? [duplicate]

If photons and gluons that have no mass travel at the speed of light and therefore have no sense of time or space due to time dilation and space contraction, what would happen if we were able to be ...
21 views

### Proper time while going up in a gravitational field

Feynman, in his book 'Surely You're Joking, Mr. Feynman' refers to a problem he once gave one of Einstein's assistants at Princeton. The problem goes something like this: You blast off in a rocket ...
1 vote
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### Use of functional derivative in derivation of Einstein Field Equations

I'm trying to understand the derivation of the Einstein field equations through the stationary action principle. I've found a pretty clear explanation on the Wikipedia article for the Einstein-Hilbert ...
11 views

### Question regarding finding Torque [closed]

In this question I am supposed to find the magnitude of $Torque$. Now the particle of mass m rotates in a circular orbit ,so it experiences $Centripetal$ $Force$. Now since the radius of the circle in ...
• 199
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### What is the wave function of a field?

I've just started QFT. While I'm learning it using the path integral formalism, I think there is another way which is the canonical representation which I didn't learn yet. Nevertheless, in Quantum ...
• 1,140
1 vote
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### A question On the deviation of the magnetic field in a solenoid using ampere's law and why we chose a specific ampereian loop

When we derive the magnetic field in a solenoid using ampere's law, we usually consider an ampereian loop such that it's bisected by one side of the transverse section of the solenoid (like in the ...
• 15
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### Find the strongest point of the magnetic field from three long conducting wires

Consider three long power lines buried in the ocean, with (from left to right) current $\frac{I}{2}, I, \frac{I}{2}$, where the direction of the current in the edge cables are negative $z$ (in to the ...
1 vote
12 views

### Is it true to say no refraction takes place when a ray comes along normal drawn to interface?

Many books and websites in our country say that there are two conditions for no refraction of light: If index of Refraction of media on both sides is same. If the ray of light falls normally on the ...
• 567
26 views

### Zeros of the Bessel function [closed]

Can someone help to find out zeros of bessel function? Pls see the equation. I know the value of f and beta. How can I find alpha? It is zeros of bessel function J1(x).
13 views

### How to proceed in this? Like about what should I take the integral [closed]

I tried solving it using general integration of the electric field from 2a to 2b and was disastrously unsuccessful. “A point charge q is situated at a distance d from one end of a thin non conducting ...
1 vote
6 views

### Partial measurement of a Two-Mode Squeezed Vacuum state

It seems that if you measure a quadrature on the first mode, let's say $\hat{q}$, on a TMSVS, the second mode will collapse into a coherent state $|q+it\rangle$ Is this true ? What is then the value ...
15 views

### In a 1D Frame is it possible for $S=|S|$? [closed]

As written before, if we use the correct units, and represent each vector with a real number and unit such as $5m$ and $-5m$ can we have $|S|=S=5m$?
23 views

### How do you know you can add thermal resistance but not thermal transmittance?

I followed through the example on this wikipedia page for calculating the thermal resistance of a composite material (a wall) composed of many layers: https://en.wikipedia.org/wiki/...
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### What could be the reason that particle like to stay in higher effective mass region?

For anisotropic effective mass specifically, position dependent effective mass of a particle in infinite square well, if we choose the mass inversely related to position. It is observed that ...
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### Can Coulomb be derived directly from Gauss?

This relates closely to questions such as Deriving Coulomb's Law from Gauss's Law and Does the Coulomb's law include more information than the Gauss's Law in electrostatics? My ...
• 47.8k
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### On the definition of projective measurement (of qubits) by choosing a basis of the state space)

What this question is about: 1)) Nielsen, M.A. and Chuang, I.L. state in their famous book (see http://dx.doi.org/10.1017/CBO9780511976667, p. 87 ff.) that projective measurements usually are defined ...
• 549
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### Potential of spherical shell when a charge is placed inside [closed]

Potential of spherical shell when a charge q is placed at a distance of r/2 from the centre of the shell