# All Questions

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### Capacitance of an arbitrary electrode configuration

I have to find the capacitance of a circuit element in three dimensions. I have the potential and charge in this cross sectional slice calculated using numerical methods. Does this value of ...
50 views

### XX coupling vs Heisenberg coupling

I am going through CURVATURE OF SPIN NETWORKS by Jonckheere et al. The first line of the abstract mentions XX coupling and Heisenberg coupling. What is the difference between these two couplings?
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### Understanding direction of magnetic field

I'm going through my notes from class on the Biot-Savart Law and looking at these examples I am wondering why the $\vec{B}$ field in the last one is in the $\hat{\phi}$ direction while the first two ...
56 views

### Legendre transformation of Entropy as a natural function of T, V, n

I have come across a question asking to get a Legendre transformation of entropy which is a natural function of 1/T, V, n starting from entropy being a natural function of T, V and n. However, I have ...
80 views

### Calculate thermal conductance of thick walls of a cuboid, given material conductivity and cube size

Note 1: This is probably as much a maths question as physics. Note 2: I am not sure if my use of the the term conductance is correct. I want to make a kiln. The walls will be thick. I can come to ...
51 views

### Doubt regarding inclined plane in feynamn lectures

I recently read something in the feynman lectures which I find difficult to understand. Imagine an inclined plane on the top of which is a smooth pulley. There is a weight hanging from the pulley and ...
28 views

### The influence of the expanding universe on the wave function

I was puzzled by a question on a physics fora about a possible connection between the expansion of the universe and the wave function. So, a photon's red shift tells us something about the expansion, ...
113 views

### Why does a superfluid climb up the wall of container?

This has been asked but I couldn't find a good answer why does super-fluid climb up the walls of container? What if the walls were too high? What forces are involved?
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### Method of determining peculiar speed of the galaxy which moves on celestial sphere and emits the light

This question is the continuation of this one. I came up with solution, but I'm not sure that it is correct. Can someone check it? Let's introduce transverse (to the observer) proper speed ...
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### when water falls to the ground and forms a puddle, where does most of the energy go?

When water falls from some height to the ground and forms a puddle, where does most of the initial potential energy go? Sound, heat, surface tension, or motion of the earth?
70 views

### In an oscillating system (SHM) with a constantly increasing amplitude, how do you relate the constant period with the highest amplitude

For example, I am working on this problem, and I don't know where to begin. All the relationships that I can think of include a constant amplitude. [A (w/w^2) sin/cos theta] Here's the problem: A ...
153 views

### Variation of power factor with impedance in a series RLC circuit

I am solving this problem from a previous year question paper A series RLC circuit has resistance of 1k at resonant frequency and half power frequencies are 20kHz and 100kHz. Determine (i) The ...
82 views

### Hysteresis loop of soft iron for different field strengths?

When calculating the work done to magnetize a material, what is the usefulness of coercivity in that calculation? If the material $Hc = 0.5\: \mathrm{A/m}$ or $Hc = 9 \times 10^5\: \mathrm{A/m}$? I ...
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### How to find proper speed (relate to homogeneous cosmic background) of the galaxy by given redshift z and observing angular velocity?

The galaxy moves of the celestial sphere. It is given that proper speed is transverse to the observer and it must to find this speed in the moment of light emission. The motion is in the FLRW ...
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### At near light speeds, are small objects in your path a problem?

A mental exercise: A space ship is accelerating toward me from far away. As it approaches me, I can observe its acceleration. This high speed ship keeps accelerating faster toward the speed of light. ...
60 views

### How do I find the unitary operator for a combined system?

I want to describe the interaction between a target and a probe and know that this is described by some unitary operator that acts on both systems. My operator needs to implement a $\pi/q$ rotation ...
43 views

### Differential equation for speed relate to the homogeneous cosmological background in FLRW metric

How to derive DE for the speed (which relate to the homogeneous cosmological background) of the observer which moves with constant proper acceleration in spatially flat FLRW universe?
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### Linearity of the critical isochore?

When looking at the pressure-temperature diagram along the critical isochore (up to quite high reduced temperatures) a very linear trend can be observed. From a theoretical point of view, is the ...
145 views

### How does the expectation value of the square of angular momentum transform under translations?

In quantum mechanics the angular momentum operator is defined as $$\mathbf{\hat L}=\mathbf{\hat x} \times \mathbf{ \hat p}$$ This definition explicitly depends on the choice of the origin of the ...
81 views

### QM : Perturbation theory with multiple operators

When doing perturbation theory in quantum mechanics, if the perturbation hamiltonian is made of three terms : $$W = W_1 +W_2 + W_3,$$ can I treat each term separately and performing perturbation ...
119 views

### Space charge limited current with and without traps

Main Question Would someone please qualitatively describe how space-charge limited conduction in oxide works, both with and without traps? I am interested in this in the context of conduction through ...
24 views

### Redshift Dependence in the Spatial Orientation of SDSS Galaxies having Redshift 0.19 to 0.20

Does redshift depend on the spatial orientation of SDSS galaxies with redshift in the range 0.19 to 0.20 ?
46 views

### What's the local law of propagation of disturbances

In Vladimir I. Arnold's Lectures on Partial Differential Equations, Chapter 3 Huygens' Principle in the Theory of Wave Propagation, which is devoted to the proof of Huygens principle (original one by ...
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### What's the size of a 'locally' flat space-time patch in a black hole background?

A black hole collapses and emits Hawking radiation with average wavelength 1/M. The observer at I^+ sees it, so do the local observers (infalling or hovering). None of these cases should violate the ...
32 views

### Modified Arrhenius equation source? year proposed?

I was curious to know when was the first time (which year) the modified Arrhenius expression was proposed: $k=A(T^n)e^{\frac{-Ea}{RT}}$. I know that the simple Arrhenius equation ...
21 views

### Calculating torque applied on domain?

How is it possible to calculate torque that is applied on a domain due to the magnetization force[H]?
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### A Global Measure on a Gravitational System

I am a computer science engineer and I am trying to simulate the gravity on my computer; several objects with different masses randomly distributed in a Three-dimensional space. I would like to ...
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### How to derive “Anti-Lagrangian” $L_4$ and $L_5$ points

In this paper on co-orbital dynamics the authors discover, numerically, "Anti-Lagrangian" solutions to the restricted 3 body problem. These Anti-Lagrange $L_4$ and $L_5$ points are 120 degrees ahead ...
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### What is the difference between single electron spin vs multiple electron spin polarization?

What is the difference between single electron spin vs multiple electron spin polarization? Particularly the case of nitrogen vacancy center in nanodiamonds.
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### Solenoid core and magnetism

I understand the core of a solenoid can help increase magnetic field produced by a given current and every metal has a specified permeability $\mu$, but what if we had a hybrid core, say 50% iron ...
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### Are the polarization field and electric field in LIH dielectric in dynamic equilibrium?

If we know that the Polarization P in LIH dielectrics is proportional to the net field inside the dielectric according to: P = ε0χeE.....(1) And we know that D = εE........(2) Does it not follow ...
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### Finding kinetic friction coefficient

A box is thrown up an incline with degree $\alpha$. the kinetic-friction coefficient is $\mu_k$. the body returns back to its start point. a. prove ...
121 views

### One-loop beta functions of the Standard Model

For my master's research on energy scale independent combinations of renormalization group equations in supersymmetric theories, I need an overview of all the one-loop beta functions of the Standard ...
69 views

### How to relate compression ratio to work input for a compressor in a heat pump

So I need to calculate the COP (Coefficient of Performance) for a 6-ton air conditioner system in terms of the compression ratio. I understand that: $$COP=\frac{Q_L}{W_{net,in}}$$ I cannot find out ...
369 views

### Elastic Ball Collision and contact angle

For a project I need to make a good simulation of balls moving around in a space. The project will be without any air drag and without losing energy in bounces. Since there is no way to lose energy ...
48 views

### What's the typical material used as a low-k ILD in semiconductors?

Semiconductor companies (namely IBM, Intel, TSMC and etc.) may use different low-k materials as inter-layer dielectric (ILD) in their fabrication process. I'm wondering what is the most typical one. ...