# All Questions

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### What is the shape of a band electron in momentum space?

Band electrons occupy adjacent sharply defined momentum states that in xyz space take the form of a spectrum of wave functions. These wave functions span the entire xyz volume of any compact unit of ...
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### Why we have to sum in all final states of hadrons

Correct if i am wrong. In deep inelastic scattering have to sum in all final sates hadrons because we do not want to detect the hadrons. all we want to detect is the electron. Am i right?
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### Pressure exerted by a gas and the ideal gas equation

While determining the pressure exerted by any gas at a temperature why do we not consider the surface area of the container in which it is kept? We say that : P=nRT/V, where, n is the no. of moles, R ...
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### deriving Bio-Savart law in QFT

It's so important and meaningful that a new theory of physics contains main equations and results of previous related ones. Maxwell theory and QFT both have explanations on electromagnetic phenomenon ...
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### Which timestep should I use for a n-body simulation of the Solar system?

I am trying to implement a n-body simulation of the Solar system and I am stuck on the issue of the simulation timestep size. At first I would like to use a simple Euler stepping scheme. Knowing that ...
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### Usage of tensors in physics

As I understand it, tensors are multi-linear maps that map vectors (and dual vectors) to real (or complex) numbers, but I'm hoping to gain some intuition as to why they are useful in physics. Is it ...
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### Why does time-independent Hamiltonian not depend on angle variable?

In Landau and Lifshitz Mechanics, $\S50$ Canonical variables a time-independent Hamiltonian is considered, and a canonical transformation is done such that adiabatic invariant $I$ becomes the new ...
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### A Formula for the Phase Difference Between the Eelectric and Magnetic Wave Oscillations?

A) Is there a formula for the phase difference between the electric and magnetic field oscillations, in vacuum, in an electromagnetic wave emitted from an antenna, as a function of the frequency the ...
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### Why would two inertial frames be distinguishable, if the coordinate of an evenet perpendicular to the motion would be different?

This question arises from the classical example: imagine a laboratory frame, and a space shuttle frame, the space shuttle moving in the laboratory frame with a constant velocity, let's say in the $x$ ...
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### Conserved quantity in a spacetime with Killing vector

I am trying to prove that that the expression $Q=-\frac{1}{\kappa}\int_{S_\infty} \nabla^i \xi^k \mathrm{d}\sigma_{ik}$ is a conserved quantity for a spacetime with Killing vector $\xi^i$ where ...
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### Can/will a proton escape the nucleus when a force is applied?

Protons are contained within the nucleus of an atom. Protons carry a positive charge. With an electric field, we can exert a force on the proton. Is it possible for the proton to escape the nucleus? ...
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### normal force on a physical pendulum

I have read and understood that a normal force has got nothing to do with torque on a physical pendulum. But I can't understand in which direction the normal force points to. Can someone help? This ...
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### As hot air rises is the cold air that rushes in pushed in or sucked in?

I seem to remember from high school, the state of equilibrium. Volumes of more molecules wanting to get to a volume of less molecules and causing a state of equilibrium. From this I believe cold air ...
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### Heating of mixture of gases with one gas barely above its boiling point

What happens when mixture of two gases is heated in a closed container? If one gas expands faster than the other and increases pressure of the container enough so that the boiling point of the other ...
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### Critical Value for Dispersion of light

If there is a ray of light moving from $n_1$ to $n_2$ you can get dispersion if $n_1$ is a function of wavelength. What angle of incidence ($\theta_1$) will maximise the dispersion? My solution so ...
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### The direction of electric field in a thin hollow cylindrical insulating shell

Consider a thin hollow cylindrical insulating shell like the one above draw in 3D-coordinate with Z-axis going out of page and is centered at the origin of XYZ axis. It has electric charge +Q ...
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### Floating of a dead body [on hold]

Why does a dead body float on water? And why does it float by making head downward? The dead body floats due to the production of gases. But how are the gases produced? And which gases are produced? ...
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### Unification of Newtonian gravity and electrostatic force

Can we not unify Newtonian gravity & electrostatic force? All properties are almost same. We can imagine the atoms of the Earth's core to become dipoles when a body is freely-falling. Thus, due to ...
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### Can charged scalar have non zero vev?

In Higgs-Kibble mechanism, if we consider a SU[2]_L doublet of complex scalar fields, then one of them is charged and the other neutral. Why does the neutral field acquire vev and not the charged one? ...
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### The state below has non-zero entanglement, but why is its discord zero? [on hold]

|ψ⟩=(|00⟩+|11⟩)/√2. after calculation, I get $\delta=cos^2(\theta)\log cos^2(\theta)+sin^2(\theta)\log sin^2(\theta)$, Its minimum value is 0, therefore the discord of the state is zero. But there is ...
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### Relation between phase of dark field and bright field images

I am trying to understand how the super-resolution technique based on Fourier Ptychography 1. In the paper, we run phase retrieval algorithms using images captured using illumination at different ...
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### Ohm's law and an ideal voltmeter

In an ideal voltmeter there is infinite resistance so because of which no current is flowing through it and the voltage reading is not affected. The ohm's law stated that V = I * R In an ideal ...
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### ${\cal N} = 4$ supersymmetry, reference request

I am looking for references for the following questions for the purposes of doing something with $S$-duality and AdS/CFT, of which I couldn't find adequately addressed in Wess and Bagger. What is ...
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### What does a one-photon state look like as a wave functional?

According to a post on a mailing list here: https://groups.google.com/d/msg/sci.physics.research/n7Ao7N9aeq0/wqgj20-jBQAJ In general, quatum states |Psi> of the electromagnetic field, no matter ...
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### Has Rovelli proven that time doesn't exist? [on hold]

Has Rovelli proven that time doesn't exist? See this paper on the Arxiv for a description of his ideas. I am reading some people argue at length, and inauspiciously, that he has. I am entirely ...
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### Does Newton's third law apply to fundamental forces?

The acceleration between two electrons A, B at 1 cm distance is a = 2533 km/s^2, therefore each of them will experience it, so they will distance each other with an acceleration of 5066 Km/s^2, ...
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### What is the size/mass of largest metal plate that was moved by casimir effect?

I learned about Casimir effect recently. Is it applicable only on very light/thin metal plates( in terms of micro/nano meters) or is the effect large enough to be noticed on mili meters scale? What is ...