# All Questions

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### Comparing quantum and natural Hamiltonian dynamical systems for the hydrogen atom: Why is quantum preferred?

The quantum model for the hydrogen atom is a Hamiltonian dynamical system based on Schrödinger operator $H$. When compared with the physical atom it has important shortcomings. First and foremost the ...
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### Where to find a Path Integral treatment of 1D Quantum Heisenberg model or Quantum Spin Chain?

All: Where to find a Path Integral treatment of 1D Quantum Heisenberg model or Quantum Spin Chain ? I would like to find a detailed calculation of path amplitude in such situation. I did some ...
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### Single slit or double slit

Are there any mathematically rigorous problems on single slit diffraction problems that I could read about, that concerns itself with more geometric optics as well? All the examples in my book are so ...
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### Quantum secret sharing

I was reading an article https://journals.aps.org/pra/abstract/10.1103/PhysRevA.71.044301 It had 3 parties Bob, Alice and Charlie. They agree on sharing a classical secret quantum mechanically. The ...
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### Einstein–Brillouin–Keller quantization rule, what does it really mean?

The Einstein–Brillouin–Keller method is a quantization rule going from classical mechanics to quantum mechanics, according to wikipedia: I have several question regarding the above description: what ...
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### how to know the (c-)parity of a particle?

As a following up to Why does the parity of a meson have a "+1" in it? I have another question: Why does the photon have a c-parity of -1? Is it due to some advanced calculation or can I ...
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### Why is force invariant under a Galilean transformation? [duplicate]

I've had a look around online, but I haven't been able to find something which answers this in a way I understand. Essentially, I'm trying to figure out why force is invariant under a Galilean ...
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### Method of resolution of forces numerical Question

The resultant of two forces F1 and F2 is at right angles to F1. Determine the angle between the forces.
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### Statics - Equilibrium of Rigid Bodies Worksheet Question

I have a standard worksheet problem involving free body diagrams and equilibrium of a rigid body. I need to calculate the reactions at A and B for the simply supported frame in the image below. I've ...
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### Linearizing Equations (Question given below):

This question is mainly asking to rewrite a different graph equation (maybe parabolic, curved, etc) and changing it to a normal linear equation in the form y = mx+b. The question 5 and 6 can be seen ...
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### Calculating natural ventilation rate of a room

How can I calculate the natural ventilation rate of a room? Which law of fluid suits best for this situation?
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### (Giamarchi) Physical meaning of $\Psi^\dagger(r)\Psi^\dagger(r+a)$

I am currently reading Giamarchi's "Quantum Physics in One Dimension". The below is the part of the book: Question: 1. Eq. (2.72) of the book defines $$O_{SU}(r)=\Psi^\dagger(r)\Psi^\dagger(r+a)$$ ...
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### Hysteresis in ferromagnets

In my text it is given that the magnetic susceptibility X = I/H but in another it was dI/dH. But second can be used to draw the hysterisis graph so I think the second must be correct. X is dependent ...
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### Fictious force energy

In a general non inertial system four fictitious forces arise: 1 coriolis Force, 2 centrifugal Force, 3 azimuthal Force, 4 "translational" Force (due to linear acceleration of the origin of the ...
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### Phase Shift in Cirac-Zoller Quantum Gate

How can we see that in the Cirac-Zoller phase gate, a $2 \pi$ laser pulse gives us a phase shift of $(-1)$? We apply a $2 \pi$ pulse tuned to the red sideband transition, which corresponds to a ...
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### Doppler effect of light

Doppler effect for light is created for relative motion . But shouldn't light always approach us at the same velocity 'c' regardless of the relative speed ?Then how does Doppler effect work ?
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### Can a field $\phi$ obey both the scalar relation and the fermi relation?

Let $L_{\text{scalar}}=\frac{1}{2}\eta^{\mu\nu}\partial_\mu \phi \partial_\nu \phi$ be the scalar lagrangian and $L_{\text{fermion}}=i\psi \gamma^u \partial_\mu \psi$ be the fermionic lagrangian. Can ...
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### Is there a difference between metal waveguides in microwave frequencies and dielectric waveguides in optical frequencies?

Do they work the same way? Do metal waveguides in MW also work through total internal reflection like in optical waveguides?
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### Energy stored in a field - isolated system

If I consider an isolated system, e.g. two masses, i know I can apply the energy conservation principle considering the kinetic energy and the gravitational potential energy of the two masses. But to ...
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### How to determine the direction of components of force while solving the problems related to hinge force?

There are two different directions of horizontal force in two different situations. Why?
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### How to formally integrate the geodesic equation given the Christoffel symbols?

Given the geodesic equation $$\ddot{x} + \Gamma^a_{\;bc}\,\dot{x}_b\dot{x}_c = 0$$ with initial conditions, say $x(\lambda=0)=0,\dot{x}(\lambda=0)=v^a$, and all the data of Christoffel symbols ...
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### Correct method for error propagation in pseudo-data approach using model

I want to compute the error on the integral over experimental data $(y_i,\delta y_i)$ in a pseudo-data approach using model ($x_i$ are assumed to be known error-less numbers). If I were using direct ...
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### How to convert $\rm kg/m^3$ to $\rm J/m^3$ for natural gas and biogas?

I want to convert from mass density to energy density: Natural gas has a density of $0.8\: \rm kg/m^3$. Biogas has $1.15\:\rm kg/m^3$. I want to convert them into $\rm J/m^3$ so that I can ...
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### Consistent calculation of the total momentum in quantum physics

When we are considering a one-dimensional case in quantum physics, we can calculate the momentum by solving the eigenvalue equation: $$-i \hbar \frac{d}{d x} \psi(x, t) = p_x \psi(x, t).$$ If we ...
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### Why is Goldstone boson not observable in the non-Hermitian QFT?

I ahve recently stumble upon a paper on the spontaneous symmetry breaking of Non-Hermitian QFT arXiv:1808.00437. On page 8 (at the end of section 3) the author claims that one can not "observe" the ...
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### Why does the parity of a meson have a “+1” in it?

The parity of a meson is defined as $P = (-1)^{L+1}$ where $L$ is the angular momentum. What does the "1" in the exponent represent?
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### Change in momentum in Impulse of deformation and reformation

I was reading some text on coefficient of restitution when I encountered this , In the following you all would notice that in Impulse of deformation for particle $m_2$ we can see that change in ...
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### Is it cold inside a black hole? [duplicate]

What is the temperature inside a black hole? It may be very cold, or very hot. Or just the surrounding temperature. Or maybe neither, because the concept of temperature makes no sense inside somehow?...
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### Measuring strong coupling constant

How can the strong coupling constant be measured?
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### Evaluating the radius of a spherical cavity that will make a glass cube just sink in water

A glass cube of side 5cm having spherical cavity within just sinks in water. If the specific gravity of glass is 2.5, what is radius of spherical cavity?
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### Role of the Yukawa potential

What is the Yukawa potential converging to zero? Afaik the strong potential rises with the distance between quarks, hence, it should rise accordingly.
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### Momentum of neutrino and beta particle [on hold]

In carbon-14 decay beta particles with end point energy 0.155MeV are emitted. A beta particle with 0.025MeV energy is emitted at 135 degree to the direction of motion of recoiling nucleus ,calculate ...
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### Does the timeline of earth changes if Gravity exceeds 15g instead of 9.8g? [on hold]

as we present a timeline to be the 4th dimensions will the dimension changes simply changing the gravity? lets say 9.8g to 15g what will be the impact on the timeline as we represent timeline as ...
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### Negative pressure in general relativity

Is there an intuitive way to understand what negative pressure means in general relativity in the same way as positive pressure can be thought to be kinetic energy of gas particles? Dark energy has ...

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